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menu__caret"></button></div><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-2 menu__list-item menu__list-item--collapsed"><div class=menu__list-item-collapsible><a class="categoryLink_byQd menu__link menu__link--sublist" tabindex=0 href=/docs/next/guide/kotlin/><span title=Kotlin class=categoryLinkLabel_W154>Kotlin</span></a><button aria-label="Expand sidebar category 'Kotlin'" aria-expanded=false type=button class="clean-btn menu__caret"></button></div><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-2 menu__list-item menu__list-item--collapsed"><div class=menu__list-item-collapsible><a class="categoryLink_byQd menu__link menu__link--sublist" tabindex=0 href=/docs/next/guide/xlang/><span title="Cross Language" class=categoryLinkLabel_W154>Cross Language</span></a><button aria-label="Expand sidebar category 'Cross Language'" aria-expanded=false type=button class="clean-btn menu__caret"></button></div></ul></ul></nav></div></div></aside><main class=docMainContainer_TBSr><div class="container padding-top--md padding-bottom--lg"><div class=row><div class="col docItemCol_VOVn"><div class="theme-doc-version-banner alert alert--warning margin-bottom--md" role=alert><div>This is unreleased documentation for <!-- -->Apache Fory™<!-- --> <b>dev</b> version.</div><div class=margin-top--md>For up-to-date documentation, see the <b><a href=/docs/guide/cpp/schema_evolution>latest version</a></b> (<!-- -->1.3.0<!-- -->).</div></div><div class=docItemContainer_Djhp><article><nav class="theme-doc-breadcrumbs breadcrumbsContainer_Z_bl" aria-label=Breadcrumbs><ul class=breadcrumbs><li class=breadcrumbs__item><a aria-label="Home page" class=breadcrumbs__link href=/><svg viewBox="0 0 24 24" class=breadcrumbHomeIcon_YNFT><path d="M10 19v-5h4v5c0 .55.45 1 1 1h3c.55 0 1-.45 1-1v-7h1.7c.46 0 .68-.57.33-.87L12.67 3.6c-.38-.34-.96-.34-1.34 0l-8.36 7.53c-.34.3-.13.87.33.87H5v7c0 .55.45 1 1 1h3c.55 0 1-.45 1-1z" fill=currentColor /></svg></a><li class=breadcrumbs__item><span class=breadcrumbs__link>Guide</span><li class=breadcrumbs__item><a class=breadcrumbs__link href=/docs/next/guide/cpp/><span>C++</span></a><li class="breadcrumbs__item breadcrumbs__item--active"><span class=breadcrumbs__link>Schema Evolution</span></ul></nav><span class="theme-doc-version-badge badge badge--secondary">Version: dev</span><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type=button class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div class="theme-doc-markdown markdown"><header><h1>Schema Evolution</h1></header><p>Apache Fory™ supports schema evolution in <strong>Compatible mode</strong>, allowing serialization and deserialization peers to have different type definitions.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=compatible-mode>Compatible Mode<a href=#compatible-mode class=hash-link aria-label="Direct link to Compatible Mode" title="Direct link to Compatible Mode" translate=no></a></h2> |
| <p>Compatible mode is enabled by default:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token macro property directive-hash" style=color:#36acaa>#</span><span class="token macro property directive keyword" style=color:#00009f>include</span><span class="token macro property" style=color:#36acaa> </span><span class="token macro property string" style=color:#e3116c>"fory/serialization/fory.h"</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>using</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>namespace</span><span class="token plain"> fory</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">serialization</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Version 1: Original schema</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">PersonV1</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string name</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int32_t</span><span class="token plain"> age</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">PersonV1</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> name</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> age</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Version 2: Added email field</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">PersonV2</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string name</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int32_t</span><span class="token plain"> age</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string email</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// NEW FIELD</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">PersonV2</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> name</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> age</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> email</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>int</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>main</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Create separate Fory instances for each schema version</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> fory_v1 </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token class-name">Fory</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>builder</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>xlang</span><span class="token punctuation" style=color:#393A34>(</span><span class="token boolean" style=color:#36acaa>true</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>build</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> fory_v2 </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token class-name">Fory</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>builder</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>xlang</span><span class="token punctuation" style=color:#393A34>(</span><span class="token boolean" style=color:#36acaa>true</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>build</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Register with the SAME type ID for schema evolution</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>constexpr</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>uint32_t</span><span class="token plain"> PERSON_TYPE_ID </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>100</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> fory_v1</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>register_struct</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">PersonV1</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">PERSON_TYPE_ID</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> fory_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>register_struct</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">PersonV2</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">PERSON_TYPE_ID</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Serialize with V1</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> PersonV1 v1</span><span class="token punctuation" style=color:#393A34>{</span><span class="token string" style=color:#e3116c>"Alice"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>30</span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> bytes </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_v1</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>serialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v1</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Deserialize as V2 - email gets default value (empty string)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> v2 </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>deserialize</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">PersonV2</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">bytes</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">name </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"Alice"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">age </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>30</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">email </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>""</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Default value for missing field</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>return</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>0</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><br/></div></code></pre></div></div> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=schema-evolution-features>Schema Evolution Features<a href=#schema-evolution-features class=hash-link aria-label="Direct link to Schema Evolution Features" title="Direct link to Schema Evolution Features" translate=no></a></h2> |
| <p>Compatible mode supports the following schema changes:</p> |
| <table><thead><tr><th>Change Type<th>Support<th>Behavior<tbody><tr><td>Add new fields<td>Supported<td>Missing fields use default values<tr><td>Remove fields<td>Supported<td>Extra fields are skipped<tr><td>Reorder fields<td>Supported<td>Fields matched by name, not position<tr><td>Change nullability<td>Supported<td><code>T</code> ↔ <code>std::optional<T></code><tr><td>Change field types<td>Selected<td>Scalar changes must be lossless<tr><td>Rename fields<td>Not supported<td>Field names must match (case-sensitive)</table> |
| <p>Compatible readers can handle selected scalar field type changes when the value is lossless. A |
| matched field can read between <code>bool</code>, <code>std::string</code>, numeric scalars, and decimal fields when the |
| converted value has the same logical value. Boolean strings must be exactly <code>"0"</code>, <code>"1"</code>, <code>"true"</code>, |
| or <code>"false"</code>. Numeric strings must use finite ASCII decimal notation without whitespace, a leading |
| <code>+</code>, Unicode digits, separators, or non-finite values such as <code>NaN</code> and <code>Infinity</code>. Numbers and |
| decimals can be read as canonical strings, and numeric widening or narrowing succeeds only when no |
| precision or range is lost. Nullable and optional field wrappers still compose with these conversions, |
| but reference-tracked scalar type changes are incompatible. Invalid strings and lossy conversions fail |
| during deserialization.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=adding-fields-backward-compatibility>Adding Fields (Backward Compatibility)<a href=#adding-fields-backward-compatibility class=hash-link aria-label="Direct link to Adding Fields (Backward Compatibility)" title="Direct link to Adding Fields (Backward Compatibility)" translate=no></a></h2> |
| <p>When deserializing old data with a new schema that has additional fields:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token comment" style=color:#999988;font-style:italic>// Old schema (V1)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">ProductV1</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string name</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>double</span><span class="token plain"> price</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">ProductV1</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> name</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> price</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// New schema (V2) with additional fields</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">ProductV2</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string name</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>double</span><span class="token plain"> price</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">vector</span><span class="token operator" style=color:#393A34><</span><span class="token plain">std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string</span><span class="token operator" style=color:#393A34>></span><span class="token plain"> tags</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// NEW</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">map</span><span class="token operator" style=color:#393A34><</span><span class="token plain">std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string</span><span class="token operator" style=color:#393A34>></span><span class="token plain"> attributes</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// NEW</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">ProductV2</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> name</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> price</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> tags</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> attributes</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Serialize V1</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">ProductV1 v1</span><span class="token punctuation" style=color:#393A34>{</span><span class="token string" style=color:#e3116c>"Laptop"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>999.99</span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> bytes </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_v1</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>serialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v1</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Deserialize as V2</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> v2 </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>deserialize</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">ProductV2</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">bytes</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">name </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"Laptop"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">price </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>999.99</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">tags</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>empty</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Default: empty vector</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">attributes</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>empty</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Default: empty map</span><br/></div></code></pre></div></div> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=removing-fields-forward-compatibility>Removing Fields (Forward Compatibility)<a href=#removing-fields-forward-compatibility class=hash-link aria-label="Direct link to Removing Fields (Forward Compatibility)" title="Direct link to Removing Fields (Forward Compatibility)" translate=no></a></h2> |
| <p>When deserializing new data with an old schema that has fewer fields:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token comment" style=color:#999988;font-style:italic>// Full schema</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">UserFull</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int64_t</span><span class="token plain"> id</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string username</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string email</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string password_hash</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int32_t</span><span class="token plain"> login_count</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">UserFull</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> id</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> username</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> email</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> password_hash</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> login_count</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Minimal schema (removed 3 fields)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">UserMinimal</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int64_t</span><span class="token plain"> id</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string username</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">UserMinimal</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> id</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> username</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Serialize full version</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">UserFull full</span><span class="token punctuation" style=color:#393A34>{</span><span class="token number" style=color:#36acaa>12345</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"johndoe"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"john@example.com"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"hash123"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>42</span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> bytes </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_full</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>serialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">full</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Deserialize as minimal - extra fields are skipped</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> minimal </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_minimal</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>deserialize</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">UserMinimal</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">bytes</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">minimal</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">id </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>12345</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">minimal</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">username </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"johndoe"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// email, password_hash, login_count are skipped</span><br/></div></code></pre></div></div> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=field-reordering>Field Reordering<a href=#field-reordering class=hash-link aria-label="Direct link to Field Reordering" title="Direct link to Field Reordering" translate=no></a></h2> |
| <p>In compatible mode, fields are matched by name, not by position:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token comment" style=color:#999988;font-style:italic>// Original field order</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">ConfigOriginal</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string host</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int32_t</span><span class="token plain"> port</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>bool</span><span class="token plain"> enable_ssl</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string protocol</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">ConfigOriginal</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> host</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> port</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> enable_ssl</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> protocol</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Reordered fields</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">ConfigReordered</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>bool</span><span class="token plain"> enable_ssl</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Moved to first</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string protocol</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Moved to second</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string host</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Moved to third</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int32_t</span><span class="token plain"> port</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Moved to last</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">ConfigReordered</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> enable_ssl</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> protocol</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> host</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> port</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Serialize with original order</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">ConfigOriginal orig</span><span class="token punctuation" style=color:#393A34>{</span><span class="token string" style=color:#e3116c>"localhost"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>8080</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token boolean" style=color:#36acaa>true</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"https"</span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> bytes </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_orig</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>serialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">orig</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Deserialize with different field order - works correctly</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> reordered </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_reord</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>deserialize</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">ConfigReordered</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">bytes</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">reordered</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">host </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"localhost"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">reordered</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">port </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>8080</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">reordered</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">enable_ssl </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token boolean" style=color:#36acaa>true</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">reordered</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">protocol </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"https"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><br/></div></code></pre></div></div> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=nested-struct-evolution>Nested Struct Evolution<a href=#nested-struct-evolution class=hash-link aria-label="Direct link to Nested Struct Evolution" title="Direct link to Nested Struct Evolution" translate=no></a></h2> |
| <p>Schema evolution works recursively for nested structs:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token comment" style=color:#999988;font-style:italic>// V1 Address</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">AddressV1</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string street</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string city</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">AddressV1</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> street</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> city</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// V2 Address with new fields</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">AddressV2</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string street</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string city</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string country</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// NEW</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string zipcode</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// NEW</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">AddressV2</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> street</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> city</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> country</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> zipcode</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// V1 Employee with V1 Address</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">EmployeeV1</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string name</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> AddressV1 home_address</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">EmployeeV1</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> name</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> home_address</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// V2 Employee with V2 Address and new field</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">EmployeeV2</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string name</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> AddressV2 home_address</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Nested struct evolved</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string employee_id</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// NEW</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">EmployeeV2</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> name</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> home_address</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> employee_id</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Register types with same IDs</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>constexpr</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>uint32_t</span><span class="token plain"> ADDRESS_TYPE_ID </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>100</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>constexpr</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>uint32_t</span><span class="token plain"> EMPLOYEE_TYPE_ID </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>101</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">fory_v1</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>register_struct</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">AddressV1</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">ADDRESS_TYPE_ID</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">fory_v1</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>register_struct</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">EmployeeV1</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">EMPLOYEE_TYPE_ID</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">fory_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>register_struct</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">AddressV2</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">ADDRESS_TYPE_ID</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">fory_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>register_struct</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">EmployeeV2</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">EMPLOYEE_TYPE_ID</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Serialize V1</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">EmployeeV1 emp_v1</span><span class="token punctuation" style=color:#393A34>{</span><span class="token string" style=color:#e3116c>"Jane Doe"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token string" style=color:#e3116c>"123 Main St"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"NYC"</span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> bytes </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_v1</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>serialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">emp_v1</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Deserialize as V2</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> emp_v2 </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>deserialize</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">EmployeeV2</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">bytes</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">emp_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">name </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"Jane Doe"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">emp_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">home_address</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">street </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"123 Main St"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">emp_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">home_address</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">city </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"NYC"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">emp_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">home_address</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">country </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>""</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Default</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">emp_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">home_address</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">zipcode </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>""</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Default</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">emp_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">employee_id </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>""</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Default</span><br/></div></code></pre></div></div> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=bidirectional-evolution>Bidirectional Evolution<a href=#bidirectional-evolution class=hash-link aria-label="Direct link to Bidirectional Evolution" title="Direct link to Bidirectional Evolution" translate=no></a></h2> |
| <p>Schema evolution works in both directions:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token comment" style=color:#999988;font-style:italic>// V2 -> V1 (downgrade)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">PersonV2 v2</span><span class="token punctuation" style=color:#393A34>{</span><span class="token string" style=color:#e3116c>"Charlie"</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>35</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"charlie@example.com"</span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> bytes </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>serialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v2</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> v1 </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory_v1</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>deserialize</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">PersonV1</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">bytes</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>value</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v1</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">name </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"Charlie"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>assert</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">v1</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">age </span><span class="token operator" style=color:#393A34>==</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>35</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// email field is discarded during deserialization</span><br/></div></code></pre></div></div> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=default-values>Default Values<a href=#default-values class=hash-link aria-label="Direct link to Default Values" title="Direct link to Default Values" translate=no></a></h2> |
| <p>When fields are missing, C++ default initialization is used:</p> |
| <table><thead><tr><th>Type<th>Default Value<tbody><tr><td><code>int8_t</code>, <code>int16_t</code>...<td><code>0</code><tr><td><code>float</code>, <code>double</code><td><code>0.0</code><tr><td><code>bool</code><td><code>false</code><tr><td><code>std::string</code><td><code>""</code><tr><td><code>std::vector<T></code><td>Empty vector<tr><td><code>std::map<K,V></code><td>Empty map<tr><td><code>std::set<T></code><td>Empty set<tr><td><code>std::optional<T></code><td><code>std::nullopt</code><tr><td>Struct types<td>Default-constructed</table> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=same-schema-optimization>Same-Schema Optimization<a href=#same-schema-optimization class=hash-link aria-label="Direct link to Same-Schema Optimization" title="Direct link to Same-Schema Optimization" translate=no></a></h2> |
| <p>Compatible mode is the default in both xlang and native mode. Set <code>compatible(false)</code> explicitly |
| only when every reader and writer always uses the same schema and you want faster serialization and smaller size:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token comment" style=color:#999988;font-style:italic>// Same-schema optimization</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> fory </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token class-name">Fory</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>builder</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>xlang</span><span class="token punctuation" style=color:#393A34>(</span><span class="token boolean" style=color:#36acaa>true</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>compatible</span><span class="token punctuation" style=color:#393A34>(</span><span class="token boolean" style=color:#36acaa>false</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>build</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Serialization/deserialization requires identical schemas</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Schema mismatches may cause errors or undefined behavior</span><br/></div></code></pre></div></div> |
| <p><strong>Use <code>compatible(false)</code> when:</strong></p> |
| <ul> |
| <li class="">Every reader and writer always uses the same schema</li> |
| <li class="">You want faster serialization and smaller size</li> |
| <li class="">For xlang payloads, every language uses the same verified schema or native types generated from Fory schema IDL</li> |
| </ul> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=per-struct-opt-out>Per-Struct Opt-Out<a href=#per-struct-opt-out class=hash-link aria-label="Direct link to Per-Struct Opt-Out" title="Direct link to Per-Struct Opt-Out" translate=no></a></h3> |
| <p>For one struct, you can opt out of evolution metadata with <code>FORY_STRUCT_EVOLVING</code> after |
| <code>FORY_STRUCT</code>:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">SameSchemaMessage</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int32_t</span><span class="token plain"> id</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">SameSchemaMessage</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> id</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token function" style=color:#d73a49>FORY_STRUCT_EVOLVING</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">SameSchemaMessage</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token boolean" style=color:#36acaa>false</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><br/></div></code></pre></div></div> |
| <p><strong>Use Compatible mode when:</strong></p> |
| <ul> |
| <li class="">Schemas may evolve independently</li> |
| <li class="">Cross-version compatibility is required</li> |
| <li class="">Different services may have different schema versions</li> |
| </ul> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=type-id-requirements>Type ID Requirements<a href=#type-id-requirements class=hash-link aria-label="Direct link to Type ID Requirements" title="Direct link to Type ID Requirements" translate=no></a></h2> |
| <p>For schema evolution to work:</p> |
| <ol> |
| <li class=""><strong>Same Type ID</strong>: Different versions of the same struct must use the same type ID</li> |
| <li class=""><strong>Consistent IDs</strong>: Type IDs must be consistent across all Fory instances</li> |
| <li class=""><strong>Register All Versions</strong>: Each Fory instance registers its own struct version</li> |
| </ol> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token keyword" style=color:#00009f>constexpr</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>uint32_t</span><span class="token plain"> PERSON_TYPE_ID </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>100</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Instance 1 uses PersonV1</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">fory_v1</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>register_struct</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">PersonV1</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">PERSON_TYPE_ID</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Instance 2 uses PersonV2</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">fory_v2</span><span class="token punctuation" style=color:#393A34>.</span><span class="token generic-function function" style=color:#d73a49>register_struct</span><span class="token generic-function generic class-name operator" style=color:#393A34><</span><span class="token generic-function generic class-name">PersonV2</span><span class="token generic-function generic class-name operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">PERSON_TYPE_ID</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Same type ID enables schema evolution</span><br/></div></code></pre></div></div> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=best-practices>Best Practices<a href=#best-practices class=hash-link aria-label="Direct link to Best Practices" title="Direct link to Best Practices" translate=no></a></h2> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=1-plan-for-evolution>1. Plan for Evolution<a href=#1-plan-for-evolution class=hash-link aria-label="Direct link to 1. Plan for Evolution" title="Direct link to 1. Plan for Evolution" translate=no></a></h3> |
| <p>Design schemas with future changes in mind:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token comment" style=color:#999988;font-style:italic>// Good: Use optional for fields that might be removed</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">Config</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string host</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int32_t</span><span class="token plain"> port</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">optional</span><span class="token operator" style=color:#393A34><</span><span class="token plain">std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string</span><span class="token operator" style=color:#393A34>></span><span class="token plain"> deprecated_field</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Can be removed later</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><br/></div></code></pre></div></div> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=2-use-meaningful-default-values>2. Use Meaningful Default Values<a href=#2-use-meaningful-default-values class=hash-link aria-label="Direct link to 2. Use Meaningful Default Values" title="Direct link to 2. Use Meaningful Default Values" translate=no></a></h3> |
| <p>Consider what default values make sense for new fields:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token keyword" style=color:#00009f>struct</span><span class="token plain"> </span><span class="token class-name">Settings</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>int32_t</span><span class="token plain"> timeout_ms</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Default: 0 (might want a sensible default)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>bool</span><span class="token plain"> enabled</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Default: false</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> std</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token plain">string mode</span><span class="token punctuation" style=color:#393A34>;</span><span class="token plain"> </span><span class="token comment" style=color:#999988;font-style:italic>// Default: "" (might want "default")</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token punctuation" style=color:#393A34>;</span><br/></div></code></pre></div></div> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=3-document-schema-versions>3. Document Schema Versions<a href=#3-document-schema-versions class=hash-link aria-label="Direct link to 3. Document Schema Versions" title="Direct link to 3. Document Schema Versions" translate=no></a></h3> |
| <p>Track schema changes for debugging:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token comment" style=color:#999988;font-style:italic>// V1: Initial schema (2024-01-01)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// V2: Added email field (2024-02-01)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// V3: Added phone, address fields (2024-03-01)</span><br/></div></code></pre></div></div> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=4-test-evolution-paths>4. Test Evolution Paths<a href=#4-test-evolution-paths class=hash-link aria-label="Direct link to 4. Test Evolution Paths" title="Direct link to 4. Test Evolution Paths" translate=no></a></h3> |
| <p>Test both upgrade and downgrade scenarios:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token comment" style=color:#999988;font-style:italic>// Test V1 -> V2</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Test V2 -> V1</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Test V1 -> V3</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token comment" style=color:#999988;font-style:italic>// Test V3 -> V1</span><br/></div></code></pre></div></div> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=xlang-schema-evolution>Xlang Schema Evolution<a href=#xlang-schema-evolution class=hash-link aria-label="Direct link to Xlang Schema Evolution" title="Direct link to Xlang Schema Evolution" translate=no></a></h2> |
| <p>Schema evolution works across languages when using xlang mode:</p> |
| <div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-cpp codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token comment" style=color:#999988;font-style:italic>// C++ with compatible mode, the default</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>auto</span><span class="token plain"> fory </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token class-name">Fory</span><span class="token double-colon punctuation" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>builder</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>xlang</span><span class="token punctuation" style=color:#393A34>(</span><span class="token boolean" style=color:#36acaa>true</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>build</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><br/></div></code></pre></div></div> |
| <div class="language-java codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-java codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token comment" style=color:#999988;font-style:italic>// Java with compatible mode, the default</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token class-name">Fory</span><span class="token plain"> fory </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token class-name">Fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>builder</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>withXlang</span><span class="token punctuation" style=color:#393A34>(</span><span class="token boolean" style=color:#36acaa>true</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>build</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><br/></div></code></pre></div></div> |
| <p>Both instances can exchange data even with different schema versions.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=related-topics>Related Topics<a href=#related-topics class=hash-link aria-label="Direct link to Related Topics" title="Direct link to Related Topics" translate=no></a></h2> |
| <ul> |
| <li class=""><a class="" href=/docs/next/guide/cpp/configuration>Configuration</a> - Enabling compatible mode</li> |
| <li class=""><a class="" href=/docs/next/guide/cpp/type_registration>Type Registration</a> - Type ID management</li> |
| <li class=""><a class="" href=/docs/next/guide/cpp/xlang_serialization>Xlang Serialization</a> - Cross-language considerations</li> |
| </ul></div><footer class="theme-doc-footer docusaurus-mt-lg"><div class="row margin-top--sm theme-doc-footer-edit-meta-row"><div class="col noPrint_WFHX"><a href=https://github.com/apache/fory-site/tree/main/docs/guide/cpp/schema-evolution.md target=_blank rel="noopener noreferrer" class=theme-edit-this-page><svg fill=currentColor height=20 width=20 viewBox="0 0 40 40" class=iconEdit_Z9Sw aria-hidden=true><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"/></g></svg>Edit this page</a></div><div class="col lastUpdated_JAkA"></div></div></footer></article><nav class="docusaurus-mt-lg pagination-nav" aria-label="Docs pages"><a class="pagination-nav__link pagination-nav__link--prev" href=/docs/next/guide/cpp/schema_metadata><div class=pagination-nav__sublabel>Previous</div><div class=pagination-nav__label>Schema Metadata</div></a><a class="pagination-nav__link pagination-nav__link--next" href=/docs/next/guide/cpp/type_registration><div class=pagination-nav__sublabel>Next</div><div class=pagination-nav__label>Type Registration</div></a></nav></div></div><div class="col col--3"><div class="tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop"><ul class="table-of-contents table-of-contents__left-border"><li><a href=#compatible-mode class="table-of-contents__link toc-highlight">Compatible Mode</a><li><a href=#schema-evolution-features class="table-of-contents__link toc-highlight">Schema Evolution Features</a><li><a href=#adding-fields-backward-compatibility class="table-of-contents__link toc-highlight">Adding Fields (Backward Compatibility)</a><li><a href=#removing-fields-forward-compatibility class="table-of-contents__link toc-highlight">Removing Fields (Forward Compatibility)</a><li><a href=#field-reordering class="table-of-contents__link toc-highlight">Field Reordering</a><li><a href=#nested-struct-evolution class="table-of-contents__link toc-highlight">Nested Struct Evolution</a><li><a href=#bidirectional-evolution class="table-of-contents__link toc-highlight">Bidirectional Evolution</a><li><a href=#default-values class="table-of-contents__link toc-highlight">Default Values</a><li><a href=#same-schema-optimization class="table-of-contents__link toc-highlight">Same-Schema Optimization</a><ul><li><a href=#per-struct-opt-out class="table-of-contents__link toc-highlight">Per-Struct Opt-Out</a></ul><li><a href=#type-id-requirements class="table-of-contents__link toc-highlight">Type ID Requirements</a><li><a href=#best-practices class="table-of-contents__link toc-highlight">Best Practices</a><ul><li><a href=#1-plan-for-evolution class="table-of-contents__link toc-highlight">1. 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