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<p class='location'>Trait VariantAccess</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#associated-types">Associated Types</a><div class="sidebar-links"><a href="#associatedtype.Error">Error</a></div><a class="sidebar-title" href="#required-methods">Required Methods</a><div class="sidebar-links"><a href="#tymethod.unit_variant">unit_variant</a><a href="#tymethod.newtype_variant_seed">newtype_variant_seed</a><a href="#tymethod.tuple_variant">tuple_variant</a><a href="#tymethod.struct_variant">struct_variant</a></div><a class="sidebar-title" href="#provided-methods">Provided Methods</a><div class="sidebar-links"><a href="#method.newtype_variant">newtype_variant</a></div><a class="sidebar-title" href="#implementors">Implementors</a></div><p class='location'><a href='../index.html'>serde</a>::<wbr><a href='index.html'>de</a></p><script>window.sidebarCurrent = {name: 'VariantAccess', ty: 'trait', relpath: ''};</script><script defer src="sidebar-items.js"></script></div>
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<h1 class='fqn'><span class='in-band'>Trait <a href='../index.html'>serde</a>::<wbr><a href='index.html'>de</a>::<wbr><a class="trait" href=''>VariantAccess</a></span><span class='out-of-band'><span id='render-detail'>
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[<span class='inner'>−</span>]
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</span><a class='srclink' href='../../src/serde/de/mod.rs.html#1997-2193' title='goto source code'>[src]</a></span></h1>
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<pre class='rust trait'>pub trait VariantAccess<'de>: <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a> {
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type <a href='#associatedtype.Error' class="type">Error</a>: <a class="trait" href="../../serde/de/trait.Error.html" title="trait serde::de::Error">Error</a>;
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fn <a href='#tymethod.unit_variant' class='fnname'>unit_variant</a>(self) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../../serde/de/trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>>;
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<div class='item-spacer'></div> fn <a href='#tymethod.newtype_variant_seed' class='fnname'>newtype_variant_seed</a><T>(self, seed: T) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T::<a class="type" href="../../serde/de/trait.DeserializeSeed.html#associatedtype.Value" title="type serde::de::DeserializeSeed::Value">Value</a>, Self::<a class="type" href="../../serde/de/trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> T: <a class="trait" href="../../serde/de/trait.DeserializeSeed.html" title="trait serde::de::DeserializeSeed">DeserializeSeed</a><'de></span>;
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<div class='item-spacer'></div> fn <a href='#tymethod.tuple_variant' class='fnname'>tuple_variant</a><V>(<br> self, <br> len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br> visitor: V<br> ) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><V::<a class="type" href="../../serde/de/trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="type" href="../../serde/de/trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> V: <a class="trait" href="../../serde/de/trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de></span>;
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<div class='item-spacer'></div> fn <a href='#tymethod.struct_variant' class='fnname'>struct_variant</a><V>(<br> self, <br> fields: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">&'static [</a>&'static <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a><a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">]</a>, <br> visitor: V<br> ) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><V::<a class="type" href="../../serde/de/trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="type" href="../../serde/de/trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> V: <a class="trait" href="../../serde/de/trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de></span>;
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||
|
||
fn <a href='#method.newtype_variant' class='fnname'>newtype_variant</a><T>(self) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, Self::<a class="type" href="../../serde/de/trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> T: <a class="trait" href="../../serde/trait.Deserialize.html" title="trait serde::Deserialize">Deserialize</a><'de></span>,
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||
{ ... }
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||
}</pre><div class='docblock'><p><code>VariantAccess</code> is a visitor that is created by the <code>Deserializer</code> and
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||
passed to the <code>Deserialize</code> to deserialize the content of a particular enum
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||
variant.</p>
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||
<h1 id="lifetime" class="section-header"><a href="#lifetime">Lifetime</a></h1>
|
||
<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>
|
||
<h1 id="example-implementation" class="section-header"><a href="#example-implementation">Example implementation</a></h1>
|
||
<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>
|
||
<h2 id='associated-types' class='small-section-header'>
|
||
Associated Types<a href='#associated-types' class='anchor'></a>
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</h2>
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<div class='methods'>
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<h3 id='associatedtype.Error' class='method'><span id='Error.t' class='invisible'><code>type <a href='#associatedtype.Error' class="type">Error</a>: <a class="trait" href="../../serde/de/trait.Error.html" title="trait serde::de::Error">Error</a></code></span></h3><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></div>
|
||
<h2 id='required-methods' class='small-section-header'>
|
||
Required Methods<a href='#required-methods' class='anchor'></a>
|
||
</h2>
|
||
<div class='methods'>
|
||
<h3 id='tymethod.unit_variant' class='method'><span id='unit_variant.v' class='invisible'><code>fn <a href='#tymethod.unit_variant' class='fnname'>unit_variant</a>(self) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../../serde/de/trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>></code></span></h3><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>
|
||
|
||
<pre class="rust rust-example-rendered">
|
||
<span class="kw">fn</span> <span class="ident">unit_variant</span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span> {
|
||
<span class="comment">// What the data actually contained; suppose it is a tuple variant.</span>
|
||
<span class="kw">let</span> <span class="ident">unexp</span> <span class="op">=</span> <span class="ident">Unexpected</span>::<span class="ident">TupleVariant</span>;
|
||
<span class="prelude-val">Err</span>(<span class="ident">de</span>::<span class="ident">Error</span>::<span class="ident">invalid_type</span>(<span class="ident">unexp</span>, <span class="kw-2">&</span><span class="string">"unit variant"</span>))
|
||
}</pre>
|
||
</div><h3 id='tymethod.newtype_variant_seed' class='method'><span id='newtype_variant_seed.v' class='invisible'><code>fn <a href='#tymethod.newtype_variant_seed' class='fnname'>newtype_variant_seed</a><T>(self, seed: T) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T::<a class="type" href="../../serde/de/trait.DeserializeSeed.html#associatedtype.Value" title="type serde::de::DeserializeSeed::Value">Value</a>, Self::<a class="type" href="../../serde/de/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="../../serde/de/trait.DeserializeSeed.html" title="trait serde::de::DeserializeSeed">DeserializeSeed</a><'de>, </span></code></span></h3><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>
|
||
|
||
<pre class="rust rust-example-rendered">
|
||
<span class="kw">fn</span> <span class="ident">newtype_variant_seed</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">_seed</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>::<span class="ident">Value</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>
|
||
<span class="kw">where</span>
|
||
<span class="ident">T</span>: <span class="ident">DeserializeSeed</span><span class="op"><</span><span class="lifetime">'de</span><span class="op">></span>,
|
||
{
|
||
<span class="comment">// What the data actually contained; suppose it is a unit variant.</span>
|
||
<span class="kw">let</span> <span class="ident">unexp</span> <span class="op">=</span> <span class="ident">Unexpected</span>::<span class="ident">UnitVariant</span>;
|
||
<span class="prelude-val">Err</span>(<span class="ident">de</span>::<span class="ident">Error</span>::<span class="ident">invalid_type</span>(<span class="ident">unexp</span>, <span class="kw-2">&</span><span class="string">"newtype variant"</span>))
|
||
}</pre>
|
||
</div><h3 id='tymethod.tuple_variant' class='method'><span id='tuple_variant.v' class='invisible'><code>fn <a href='#tymethod.tuple_variant' class='fnname'>tuple_variant</a><V>(<br> self, <br> len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br> visitor: V<br>) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><V::<a class="type" href="../../serde/de/trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="type" href="../../serde/de/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="../../serde/de/trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de>, </span></code></span></h3><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>
|
||
|
||
<pre class="rust rust-example-rendered">
|
||
<span class="kw">fn</span> <span class="ident">tuple_variant</span><span class="op"><</span><span class="ident">V</span><span class="op">></span>(
|
||
<span class="self">self</span>,
|
||
<span class="ident">_len</span>: <span class="ident">usize</span>,
|
||
<span class="ident">_visitor</span>: <span class="ident">V</span>,
|
||
) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">V</span>::<span class="ident">Value</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>
|
||
<span class="kw">where</span>
|
||
<span class="ident">V</span>: <span class="ident">Visitor</span><span class="op"><</span><span class="lifetime">'de</span><span class="op">></span>,
|
||
{
|
||
<span class="comment">// What the data actually contained; suppose it is a unit variant.</span>
|
||
<span class="kw">let</span> <span class="ident">unexp</span> <span class="op">=</span> <span class="ident">Unexpected</span>::<span class="ident">UnitVariant</span>;
|
||
<span class="prelude-val">Err</span>(<span class="ident">de</span>::<span class="ident">Error</span>::<span class="ident">invalid_type</span>(<span class="ident">unexp</span>, <span class="kw-2">&</span><span class="string">"tuple variant"</span>))
|
||
}</pre>
|
||
</div><h3 id='tymethod.struct_variant' class='method'><span id='struct_variant.v' class='invisible'><code>fn <a href='#tymethod.struct_variant' class='fnname'>struct_variant</a><V>(<br> self, <br> fields: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">&'static [</a>&'static <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a><a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">]</a>, <br> visitor: V<br>) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><V::<a class="type" href="../../serde/de/trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="type" href="../../serde/de/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="../../serde/de/trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de>, </span></code></span></h3><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>
|
||
|
||
<pre class="rust rust-example-rendered">
|
||
<span class="kw">fn</span> <span class="ident">struct_variant</span><span class="op"><</span><span class="ident">V</span><span class="op">></span>(
|
||
<span class="self">self</span>,
|
||
<span class="ident">_fields</span>: <span class="kw-2">&</span><span class="lifetime">'static</span> [<span class="kw-2">&</span><span class="lifetime">'static</span> <span class="ident">str</span>],
|
||
<span class="ident">_visitor</span>: <span class="ident">V</span>,
|
||
) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">V</span>::<span class="ident">Value</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>
|
||
<span class="kw">where</span>
|
||
<span class="ident">V</span>: <span class="ident">Visitor</span><span class="op"><</span><span class="lifetime">'de</span><span class="op">></span>,
|
||
{
|
||
<span class="comment">// What the data actually contained; suppose it is a unit variant.</span>
|
||
<span class="kw">let</span> <span class="ident">unexp</span> <span class="op">=</span> <span class="ident">Unexpected</span>::<span class="ident">UnitVariant</span>;
|
||
<span class="prelude-val">Err</span>(<span class="ident">de</span>::<span class="ident">Error</span>::<span class="ident">invalid_type</span>(<span class="ident">unexp</span>, <span class="kw-2">&</span><span class="string">"struct variant"</span>))
|
||
}</pre>
|
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</div></div>
|
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<h2 id='provided-methods' class='small-section-header'>
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Provided Methods<a href='#provided-methods' class='anchor'></a>
|
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</h2>
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<div class='methods'>
|
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<h3 id='method.newtype_variant' class='method'><span id='newtype_variant.v' class='invisible'><code>fn <a href='#method.newtype_variant' class='fnname'>newtype_variant</a><T>(self) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, Self::<a class="type" href="../../serde/de/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="../../serde/trait.Deserialize.html" title="trait serde::Deserialize">Deserialize</a><'de>, </span></code></span></h3><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>
|
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</div></div>
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Implementors<a href='#implementors' class='anchor'></a>
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<code>struct</code>, <code>enum</code>,
|
||
<code>trait</code>, <code>type</code>, <code>macro</code>,
|
||
and <code>const</code>.
|
||
</p>
|
||
|
||
<p>
|
||
Search functions by type signature (e.g.
|
||
<code>vec -> usize</code> or <code>* -> vec</code>)
|
||
</p>
|
||
</div>
|
||
</div>
|
||
</aside>
|
||
|
||
|
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|
||
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|
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