| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="`VariantAccess` is a visitor that is created by the `Deserializer` and passed to the `Deserialize` to deserialize the content of a particular enum variant."><meta name="keywords" content="rust, rustlang, rust-lang, VariantAccess"><title>VariantAccess in serde::de - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="sidebar-items.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc trait"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../../serde/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../../serde/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a><h2 class="location"><a href="#">VariantAccess</a></h2><div class="sidebar-elems"><section><h3><a href="#required-associated-types">Required Associated Types</a></h3><ul class="block"><li><a href="#associatedtype.Error">Error</a></li></ul><h3><a href="#required-methods">Required Methods</a></h3><ul class="block"><li><a href="#tymethod.newtype_variant_seed">newtype_variant_seed</a></li><li><a href="#tymethod.struct_variant">struct_variant</a></li><li><a href="#tymethod.tuple_variant">tuple_variant</a></li><li><a href="#tymethod.unit_variant">unit_variant</a></li></ul><h3><a href="#provided-methods">Provided Methods</a></h3><ul class="block"><li><a href="#method.newtype_variant">newtype_variant</a></li></ul><h3><a href="#implementors">Implementors</a></h3></section><h2><a href="index.html">In serde::de</a></h2></div></nav><main><div class="width-limiter"><nav class="sub"><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn">Trait <a href="../index.html">serde</a>::<wbr><a href="index.html">de</a>::<wbr><a class="trait" href="#">VariantAccess</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../../clipboard.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="srclink" href="../../src/serde/de/mod.rs.html#2028-2224">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="item-decl"><pre class="rust trait"><code>pub trait VariantAccess<'de>: Sized { |
| type <a href="#associatedtype.Error" class="associatedtype">Error</a>: <a class="trait" href="trait.Error.html" title="trait serde::de::Error">Error</a>; |
| |
| fn <a href="#tymethod.unit_variant" class="fnname">unit_variant</a>(self) -> Result<(), Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>>; |
| <span class="item-spacer"></span> fn <a href="#tymethod.newtype_variant_seed" class="fnname">newtype_variant_seed</a><T>(self, seed: T) -> Result<T::<a class="associatedtype" href="trait.DeserializeSeed.html#associatedtype.Value" title="type serde::de::DeserializeSeed::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> T: <a class="trait" href="trait.DeserializeSeed.html" title="trait serde::de::DeserializeSeed">DeserializeSeed</a><'de></span>; |
| <span class="item-spacer"></span> fn <a href="#tymethod.tuple_variant" class="fnname">tuple_variant</a><V>(<br> self,<br> len: usize,<br> visitor: V<br> ) -> Result<V::<a class="associatedtype" href="trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> V: <a class="trait" href="trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de></span>; |
| <span class="item-spacer"></span> fn <a href="#tymethod.struct_variant" class="fnname">struct_variant</a><V>(<br> self,<br> fields: &'static [&'static str],<br> visitor: V<br> ) -> Result<V::<a class="associatedtype" href="trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> V: <a class="trait" href="trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de></span>; |
| |
| fn <a href="#method.newtype_variant" class="fnname">newtype_variant</a><T>(self) -> Result<T, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> T: <a class="trait" href="../trait.Deserialize.html" title="trait serde::Deserialize">Deserialize</a><'de></span>, |
| { ... } |
| }</code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p><code>VariantAccess</code> is a visitor that is created by the <code>Deserializer</code> and |
| passed to the <code>Deserialize</code> to deserialize the content of a particular enum |
| variant.</p> |
| <h2 id="lifetime"><a href="#lifetime">Lifetime</a></h2> |
| <p>The <code>'de</code> lifetime of this trait is the lifetime of data that may be |
| borrowed by the deserialized enum variant. See the page <a href="https://serde.rs/lifetimes.html">Understanding |
| deserializer lifetimes</a> for a more detailed explanation of these lifetimes.</p> |
| <h2 id="example-implementation"><a href="#example-implementation">Example implementation</a></h2> |
| <p>The <a href="https://serde.rs/data-format.html">example data format</a> presented on the website demonstrates an |
| implementation of <code>VariantAccess</code> for a basic JSON data format.</p> |
| </div></details><h2 id="required-associated-types" class="small-section-header">Required Associated Types<a href="#required-associated-types" class="anchor"></a></h2><div class="methods"><details class="rustdoc-toggle method-toggle" open><summary><section id="associatedtype.Error" class="method has-srclink"><a class="srclink rightside" href="../../src/serde/de/mod.rs.html#2031">source</a><h4 class="code-header">type <a href="#associatedtype.Error" class="associatedtype">Error</a>: <a class="trait" href="trait.Error.html" title="trait serde::de::Error">Error</a></h4></section></summary><div class="docblock"><p>The error type that can be returned if some error occurs during |
| deserialization. Must match the error type of our <code>EnumAccess</code>.</p> |
| </div></details></div><h2 id="required-methods" class="small-section-header">Required Methods<a href="#required-methods" class="anchor"></a></h2><div class="methods"><details class="rustdoc-toggle method-toggle" open><summary><section id="tymethod.unit_variant" class="method has-srclink"><a class="srclink rightside" href="../../src/serde/de/mod.rs.html#2068">source</a><h4 class="code-header">fn <a href="#tymethod.unit_variant" class="fnname">unit_variant</a>(self) -> Result<(), Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>></h4></section></summary><div class="docblock"><p>Called when deserializing a variant with no values.</p> |
| <p>If the data contains a different type of variant, the following |
| <code>invalid_type</code> error should be constructed:</p> |
| |
| <div class="example-wrap edition"><div class='tooltip' data-edition="2018">ⓘ</div><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>unit_variant(<span class="self">self</span>) -> <span class="prelude-ty">Result</span><(), <span class="self">Self</span>::Error> { |
| <span class="comment">// What the data actually contained; suppose it is a tuple variant. |
| </span><span class="kw">let </span>unexp = Unexpected::TupleVariant; |
| <span class="prelude-val">Err</span>(de::Error::invalid_type(unexp, <span class="kw-2">&</span><span class="string">"unit variant"</span>)) |
| }</code></pre></div> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="tymethod.newtype_variant_seed" class="method has-srclink"><a class="srclink rightside" href="../../src/serde/de/mod.rs.html#2110-2112">source</a><h4 class="code-header">fn <a href="#tymethod.newtype_variant_seed" class="fnname">newtype_variant_seed</a><T>(self, seed: T) -> Result<T::<a class="associatedtype" href="trait.DeserializeSeed.html#associatedtype.Value" title="type serde::de::DeserializeSeed::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><span class="where fmt-newline">where<br> T: <a class="trait" href="trait.DeserializeSeed.html" title="trait serde::de::DeserializeSeed">DeserializeSeed</a><'de>,</span></h4></section></summary><div class="docblock"><p>Called when deserializing a variant with a single value.</p> |
| <p><code>Deserialize</code> implementations should typically use |
| <code>VariantAccess::newtype_variant</code> instead.</p> |
| <p>If the data contains a different type of variant, the following |
| <code>invalid_type</code> error should be constructed:</p> |
| |
| <div class="example-wrap edition"><div class='tooltip' data-edition="2018">ⓘ</div><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>newtype_variant_seed<T>(<span class="self">self</span>, _seed: T) -> <span class="prelude-ty">Result</span><T::Value, <span class="self">Self</span>::Error> |
| <span class="kw">where |
| </span>T: DeserializeSeed<<span class="lifetime">'de</span>>, |
| { |
| <span class="comment">// What the data actually contained; suppose it is a unit variant. |
| </span><span class="kw">let </span>unexp = Unexpected::UnitVariant; |
| <span class="prelude-val">Err</span>(de::Error::invalid_type(unexp, <span class="kw-2">&</span><span class="string">"newtype variant"</span>)) |
| }</code></pre></div> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="tymethod.tuple_variant" class="method has-srclink"><a class="srclink rightside" href="../../src/serde/de/mod.rs.html#2170-2172">source</a><h4 class="code-header">fn <a href="#tymethod.tuple_variant" class="fnname">tuple_variant</a><V>(self, len: usize, visitor: V) -> Result<V::<a class="associatedtype" href="trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><span class="where fmt-newline">where<br> V: <a class="trait" href="trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de>,</span></h4></section></summary><div class="docblock"><p>Called when deserializing a tuple-like variant.</p> |
| <p>The <code>len</code> is the number of fields expected in the tuple variant.</p> |
| <p>If the data contains a different type of variant, the following |
| <code>invalid_type</code> error should be constructed:</p> |
| |
| <div class="example-wrap edition"><div class='tooltip' data-edition="2018">ⓘ</div><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>tuple_variant<V>( |
| <span class="self">self</span>, |
| _len: usize, |
| _visitor: V, |
| ) -> <span class="prelude-ty">Result</span><V::Value, <span class="self">Self</span>::Error> |
| <span class="kw">where |
| </span>V: Visitor<<span class="lifetime">'de</span>>, |
| { |
| <span class="comment">// What the data actually contained; suppose it is a unit variant. |
| </span><span class="kw">let </span>unexp = Unexpected::UnitVariant; |
| <span class="prelude-val">Err</span>(de::Error::invalid_type(unexp, <span class="kw-2">&</span><span class="string">"tuple variant"</span>)) |
| }</code></pre></div> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="tymethod.struct_variant" class="method has-srclink"><a class="srclink rightside" href="../../src/serde/de/mod.rs.html#2217-2223">source</a><h4 class="code-header">fn <a href="#tymethod.struct_variant" class="fnname">struct_variant</a><V>(<br> self,<br> fields: &'static [&'static str],<br> visitor: V<br>) -> Result<V::<a class="associatedtype" href="trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><span class="where fmt-newline">where<br> V: <a class="trait" href="trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de>,</span></h4></section></summary><div class="docblock"><p>Called when deserializing a struct-like variant.</p> |
| <p>The <code>fields</code> are the names of the fields of the struct variant.</p> |
| <p>If the data contains a different type of variant, the following |
| <code>invalid_type</code> error should be constructed:</p> |
| |
| <div class="example-wrap edition"><div class='tooltip' data-edition="2018">ⓘ</div><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>struct_variant<V>( |
| <span class="self">self</span>, |
| _fields: <span class="kw-2">&</span><span class="lifetime">'static </span>[<span class="kw-2">&</span><span class="lifetime">'static </span>str], |
| _visitor: V, |
| ) -> <span class="prelude-ty">Result</span><V::Value, <span class="self">Self</span>::Error> |
| <span class="kw">where |
| </span>V: Visitor<<span class="lifetime">'de</span>>, |
| { |
| <span class="comment">// What the data actually contained; suppose it is a unit variant. |
| </span><span class="kw">let </span>unexp = Unexpected::UnitVariant; |
| <span class="prelude-val">Err</span>(de::Error::invalid_type(unexp, <span class="kw-2">&</span><span class="string">"struct variant"</span>)) |
| }</code></pre></div> |
| </div></details></div><h2 id="provided-methods" class="small-section-header">Provided Methods<a href="#provided-methods" class="anchor"></a></h2><div class="methods"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.newtype_variant" class="method has-srclink"><a class="srclink rightside" href="../../src/serde/de/mod.rs.html#2120-2125">source</a><h4 class="code-header">fn <a href="#method.newtype_variant" class="fnname">newtype_variant</a><T>(self) -> Result<T, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><span class="where fmt-newline">where<br> T: <a class="trait" href="../trait.Deserialize.html" title="trait serde::Deserialize">Deserialize</a><'de>,</span></h4></section></summary><div class="docblock"><p>Called when deserializing a variant with a single value.</p> |
| <p>This method exists as a convenience for <code>Deserialize</code> implementations. |
| <code>VariantAccess</code> implementations should not override the default |
| behavior.</p> |
| </div></details></div><h2 id="implementors" class="small-section-header">Implementors<a href="#implementors" class="anchor"></a></h2><div id="implementors-list"></div><script src="../../implementors/serde/de/trait.VariantAccess.js" async></script></section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="serde" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
