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class=linkLabel_WmDU>Custom Serializers</span></a><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class=menu__link tabindex=0 href=/docs/next/guide/dart/web_platform_support><span title="Web Platform Support" class=linkLabel_WmDU>Web Platform Support</span></a><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class=menu__link tabindex=0 href=/docs/next/guide/dart/troubleshooting><span title=Troubleshooting class=linkLabel_WmDU>Troubleshooting</span></a><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class=menu__link tabindex=0 href=/docs/next/guide/dart/grpc_support><span title="gRPC Support" class=linkLabel_WmDU>gRPC Support</span></a></ul><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/scala/><span title=Scala class=categoryLinkLabel_W154>Scala</span></a><button aria-label="Expand sidebar category 'Scala'" 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/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/dart/custom_serializers>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/dart/><span>Dart</span></a><li class="breadcrumbs__item breadcrumbs__item--active"><span class=breadcrumbs__link>Custom Serializers</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>Custom Serializers</h1></header><p>A custom serializer lets you control exactly how a type is encoded and decoded. You only need one when:</p> | |
| <ul> | |
| <li class="">the type comes from a package you cannot modify and cannot be annotated with <code>@ForyStruct()</code></li> | |
| <li class="">you need a completely custom binary layout</li> | |
| <li class="">you are implementing a union/discriminated type</li> | |
| </ul> | |
| <p>For your own models, <code>@ForyStruct()</code> with code generation is almost always the better choice.</p> | |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=implement-serializert>Implement <code>Serializer<T></code><a href=#implement-serializert class=hash-link aria-label="Direct link to implement-serializert" title="Direct link to implement-serializert" translate=no></a></h2> | |
| <p>Subclass <code>Serializer<T></code> and implement <code>write</code> and <code>read</code>. Use <code>context.buffer</code> to read and write raw bytes:</p> | |
| <div class="language-dart codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-dart 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>import</span><span class="token plain"> </span><span class="token string-literal string" style=color:#e3116c>'package:fory/fory.dart'</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>final</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token class-name">Person</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 class-name">Person</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>this</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"> </span><span class="token keyword" style=color:#00009f>this</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 keyword" style=color:#00009f>final</span><span class="token plain"> </span><span class="token class-name">String</span><span class="token plain"> 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>final</span><span class="token plain"> int 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 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>final</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token class-name">PersonSerializer</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>extends</span><span class="token plain"> </span><span class="token class-name">Serializer</span><span class="token generics punctuation" style=color:#393A34><</span><span class="token generics class-name">Person</span><span class="token generics 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 keyword" style=color:#00009f>const</span><span class="token plain"> </span><span class="token class-name">PersonSerializer</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 metadata function" style=color:#d73a49>@override</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>void</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>write</span><span class="token punctuation" style=color:#393A34>(</span><span class="token class-name">WriteContext</span><span class="token plain"> context</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token class-name">Person</span><span class="token plain"> value</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 keyword" style=color:#00009f>final</span><span class="token plain"> buffer </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> context</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">buffer</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"> buffer</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>writeUtf8</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">value</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 punctuation" style=color:#393A34>;</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> buffer</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>writeInt64FromInt</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">value</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"> </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 metadata function" style=color:#d73a49>@override</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">Person</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>read</span><span class="token punctuation" style=color:#393A34>(</span><span class="token class-name">ReadContext</span><span class="token plain"> context</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 keyword" style=color:#00009f>final</span><span class="token plain"> buffer </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> context</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">buffer</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>return</span><span class="token plain"> </span><span class="token class-name">Person</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">buffer</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>readUtf8</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"> buffer</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>readInt64AsInt</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><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 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> | |
| <p>Register the serializer before you use it:</p> | |
| <div class="language-dart codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-dart 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>final</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 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</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>registerSerializer</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 class-name">Person</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>const</span><span class="token plain"> </span><span class="token class-name">PersonSerializer</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"> name</span><span class="token punctuation" style=color:#393A34>:</span><span class="token plain"> </span><span class="token string-literal string" style=color:#e3116c>'example.Person'</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><br/></div></code></pre></div></div> | |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=writing-nested-objects>Writing Nested Objects<a href=#writing-nested-objects class=hash-link aria-label="Direct link to Writing Nested Objects" title="Direct link to Writing Nested Objects" translate=no></a></h2> | |
| <p>When your serializer has a field that is itself a Fory-managed type, use <code>context.writeRef</code> and <code>context.readRef</code> rather than calling <code>fory.serialize</code> recursively. This keeps reference tracking correct and avoids writing a full root frame inside a nested payload.</p> | |
| <div class="language-dart codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-dart codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token metadata function" style=color:#d73a49>@override</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>void</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>write</span><span class="token punctuation" style=color:#393A34>(</span><span class="token class-name">WriteContext</span><span class="token plain"> context</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token class-name">Wrapper</span><span class="token plain"> value</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"> context</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>writeRef</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">value</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">child</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 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 metadata function" style=color:#d73a49>@override</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">Wrapper</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>read</span><span class="token punctuation" style=color:#393A34>(</span><span class="token class-name">ReadContext</span><span class="token plain"> context</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 keyword" style=color:#00009f>return</span><span class="token plain"> </span><span class="token class-name">Wrapper</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">context</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>readRef</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 operator" style=color:#393A34>as</span><span class="token plain"> </span><span class="token class-name">Child</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><br/></div></code></pre></div></div> | |
| <p>If you do not need reference identity tracking for a nested value (i.e., you know the value will never appear more than once in a graph), use <code>writeNonRef</code>:</p> | |
| <div class="language-dart codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-dart codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">context</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>writeNonRef</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">value</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">child</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=unions>Unions<a href=#unions class=hash-link aria-label="Direct link to Unions" title="Direct link to Unions" translate=no></a></h2> | |
| <p>For a discriminated/tagged union, extend <code>UnionSerializer<T></code> instead of <code>Serializer<T></code>. Write a discriminant value first, then the active variant; read the discriminant and dispatch accordingly.</p> | |
| <div class="language-dart codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-dart 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>final</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token class-name">ShapeSerializer</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>extends</span><span class="token plain"> </span><span class="token class-name">UnionSerializer</span><span class="token generics punctuation" style=color:#393A34><</span><span class="token generics class-name">Shape</span><span class="token generics 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 keyword" style=color:#00009f>const</span><span class="token plain"> </span><span class="token class-name">ShapeSerializer</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 metadata function" style=color:#d73a49>@override</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>void</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>write</span><span class="token punctuation" style=color:#393A34>(</span><span class="token class-name">WriteContext</span><span class="token plain"> context</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token class-name">Shape</span><span class="token plain"> value</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>// write active variant</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 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 metadata function" style=color:#d73a49>@override</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">Shape</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>read</span><span class="token punctuation" style=color:#393A34>(</span><span class="token class-name">ReadContext</span><span class="token plain"> context</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>// read discriminant, return correct variant</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>throw</span><span class="token plain"> </span><span class="token class-name">UnimplementedError</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 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=circular-references-in-custom-serializers>Circular References in Custom Serializers<a href=#circular-references-in-custom-serializers class=hash-link aria-label="Direct link to Circular References in Custom Serializers" title="Direct link to Circular References in Custom Serializers" translate=no></a></h2> | |
| <p>If your serializer can encounter circular object graphs, bind the object to the reference tracker <strong>before</strong> reading its nested fields:</p> | |
| <div class="language-dart codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-dart 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>final</span><span class="token plain"> value </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token class-name">Node</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 plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">context</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>reference</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">value</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>// register the object first</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">value</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">next </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> context</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>readRef</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 operator" style=color:#393A34>as</span><span class="token plain"> </span><span class="token class-name">Node</span><span class="token operator" 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>// now nested reads can refer back to it</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>return</span><span class="token plain"> value</span><span class="token punctuation" style=color:#393A34>;</span><br/></div></code></pre></div></div> | |
| <p>Skipping this step causes back-references to that object to resolve to <code>null</code>.</p> | |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=tips>Tips<a href=#tips class=hash-link aria-label="Direct link to Tips" title="Direct link to Tips" translate=no></a></h2> | |
| <ul> | |
| <li class="">Use <code>context.buffer</code> for direct byte reads/writes in hot paths.</li> | |
| <li class="">Register the serializer with the same identity (<code>id</code> or <code>name</code>) on every side.</li> | |
| </ul> | |
| <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/dart/type_registration>Type Registration</a></li> | |
| <li class=""><a class="" href=/docs/next/guide/dart/xlang_serialization>Xlang Serialization</a></li> | |
| <li class=""><a class="" href=/docs/next/guide/dart/troubleshooting>Troubleshooting</a></li> | |
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