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<p class='location'>Trait SerializeMap</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.Ok">Ok</a><a href="#associatedtype.Error">Error</a></div><a class="sidebar-title" href="#required-methods">Required Methods</a><div class="sidebar-links"><a href="#tymethod.serialize_key">serialize_key</a><a href="#tymethod.serialize_value">serialize_value</a><a href="#tymethod.end">end</a></div><a class="sidebar-title" href="#provided-methods">Provided Methods</a><div class="sidebar-links"><a href="#method.serialize_entry">serialize_entry</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'>ser</a></p><script>window.sidebarCurrent = {name: 'SerializeMap', 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'>ser</a>::<wbr><a class="trait" href=''>SerializeMap</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a class='srclink' href='../../src/serde/ser/mod.rs.html#1860-1919' title='goto source code'>[src]</a></span></h1>
<pre class='rust trait'>pub trait SerializeMap {
type <a href='#associatedtype.Ok' class="type">Ok</a>;
type <a href='#associatedtype.Error' class="type">Error</a>: <a class="trait" href="../../serde/ser/trait.Error.html" title="trait serde::ser::Error">Error</a>;
fn <a href='#tymethod.serialize_key' class='fnname'>serialize_key</a>&lt;T:&nbsp;?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>&gt;(&amp;mut self, key: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;</a>T) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../../serde/ser/trait.SerializeMap.html#associatedtype.Error" title="type serde::ser::SerializeMap::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="../../serde/trait.Serialize.html" title="trait serde::Serialize">Serialize</a></span>;
<div class='item-spacer'></div> fn <a href='#tymethod.serialize_value' class='fnname'>serialize_value</a>&lt;T:&nbsp;?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;value: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;</a>T<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../../serde/ser/trait.SerializeMap.html#associatedtype.Error" title="type serde::ser::SerializeMap::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="../../serde/trait.Serialize.html" title="trait serde::Serialize">Serialize</a></span>;
<div class='item-spacer'></div> fn <a href='#tymethod.end' class='fnname'>end</a>(self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;Self::<a class="type" href="../../serde/ser/trait.SerializeMap.html#associatedtype.Ok" title="type serde::ser::SerializeMap::Ok">Ok</a>, Self::<a class="type" href="../../serde/ser/trait.SerializeMap.html#associatedtype.Error" title="type serde::ser::SerializeMap::Error">Error</a>&gt;;
fn <a href='#method.serialize_entry' class='fnname'>serialize_entry</a>&lt;K:&nbsp;?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, V:&nbsp;?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;key: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;</a>K, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;value: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;</a>V<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../../serde/ser/trait.SerializeMap.html#associatedtype.Error" title="type serde::ser::SerializeMap::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;K: <a class="trait" href="../../serde/trait.Serialize.html" title="trait serde::Serialize">Serialize</a>,<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;V: <a class="trait" href="../../serde/trait.Serialize.html" title="trait serde::Serialize">Serialize</a></span>,
{ ... }
}</pre><div class='docblock'><p>Returned from <code>Serializer::serialize_map</code>.</p>
<h1 id="example-use" class="section-header"><a href="#example-use">Example use</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">serde</span>::<span class="ident">ser</span>::{<span class="ident">Serialize</span>, <span class="ident">Serializer</span>, <span class="ident">SerializeMap</span>};
<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">K</span>, <span class="ident">V</span><span class="op">&gt;</span> <span class="ident">Serialize</span> <span class="kw">for</span> <span class="ident">HashMap</span><span class="op">&lt;</span><span class="ident">K</span>, <span class="ident">V</span><span class="op">&gt;</span>
<span class="kw">where</span>
<span class="ident">K</span>: <span class="ident">Serialize</span>,
<span class="ident">V</span>: <span class="ident">Serialize</span>,
{
<span class="kw">fn</span> <span class="ident">serialize</span><span class="op">&lt;</span><span class="ident">S</span><span class="op">&gt;</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">serializer</span>: <span class="ident">S</span>) <span class="op">-&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">S</span>::<span class="prelude-val">Ok</span>, <span class="ident">S</span>::<span class="ident">Error</span><span class="op">&gt;</span>
<span class="kw">where</span>
<span class="ident">S</span>: <span class="ident">Serializer</span>,
{
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">map</span> <span class="op">=</span> <span class="ident">serializer</span>.<span class="ident">serialize_map</span>(<span class="prelude-val">Some</span>(<span class="self">self</span>.<span class="ident">len</span>()))<span class="question-mark">?</span>;
<span class="kw">for</span> (<span class="ident">k</span>, <span class="ident">v</span>) <span class="kw">in</span> <span class="self">self</span> {
<span class="ident">map</span>.<span class="ident">serialize_entry</span>(<span class="ident">k</span>, <span class="ident">v</span>)<span class="question-mark">?</span>;
}
<span class="ident">map</span>.<span class="ident">end</span>()
}
}</pre>
<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>SerializeMap</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>
</h2>
<div class='methods'>
<h3 id='associatedtype.Ok' class='method'><span id='Ok.t' class='invisible'><code>type <a href='#associatedtype.Ok' class="type">Ok</a></code></span></h3><div class='docblock'><p>Must match the <code>Ok</code> type of our <code>Serializer</code>.</p>
</div><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/ser/trait.Error.html" title="trait serde::ser::Error">Error</a></code></span></h3><div class='docblock'><p>Must match the <code>Error</code> type of our <code>Serializer</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.serialize_key' class='method'><span id='serialize_key.v' class='invisible'><code>fn <a href='#tymethod.serialize_key' class='fnname'>serialize_key</a>&lt;T:&nbsp;?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>&gt;(&amp;mut self, key: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;</a>T) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../../serde/ser/trait.SerializeMap.html#associatedtype.Error" title="type serde::ser::SerializeMap::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="../../serde/trait.Serialize.html" title="trait serde::Serialize">Serialize</a>,&nbsp;</span></code></span></h3><div class='docblock'><p>Serialize a map key.</p>
<p>If possible, <code>Serialize</code> implementations are encouraged to use
<code>serialize_entry</code> instead as it may be implemented more efficiently in
some formats compared to a pair of calls to <code>serialize_key</code> and
<code>serialize_value</code>.</p>
</div><h3 id='tymethod.serialize_value' class='method'><span id='serialize_value.v' class='invisible'><code>fn <a href='#tymethod.serialize_value' class='fnname'>serialize_value</a>&lt;T:&nbsp;?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>&gt;(&amp;mut self, value: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;</a>T) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../../serde/ser/trait.SerializeMap.html#associatedtype.Error" title="type serde::ser::SerializeMap::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="../../serde/trait.Serialize.html" title="trait serde::Serialize">Serialize</a>,&nbsp;</span></code></span></h3><div class='docblock'><p>Serialize a map value.</p>
<h1 id="panics" class="section-header"><a href="#panics">Panics</a></h1>
<p>Calling <code>serialize_value</code> before <code>serialize_key</code> is incorrect and is
allowed to panic or produce bogus results.</p>
</div><h3 id='tymethod.end' class='method'><span id='end.v' class='invisible'><code>fn <a href='#tymethod.end' class='fnname'>end</a>(self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;Self::<a class="type" href="../../serde/ser/trait.SerializeMap.html#associatedtype.Ok" title="type serde::ser::SerializeMap::Ok">Ok</a>, Self::<a class="type" href="../../serde/ser/trait.SerializeMap.html#associatedtype.Error" title="type serde::ser::SerializeMap::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Finish serializing a map.</p>
</div></div>
<h2 id='provided-methods' class='small-section-header'>
Provided Methods<a href='#provided-methods' class='anchor'></a>
</h2>
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<h3 id='method.serialize_entry' class='method'><span id='serialize_entry.v' class='invisible'><code>fn <a href='#method.serialize_entry' class='fnname'>serialize_entry</a>&lt;K:&nbsp;?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, V:&nbsp;?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;key: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;</a>K, <br>&nbsp;&nbsp;&nbsp;&nbsp;value: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;</a>V<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../../serde/ser/trait.SerializeMap.html#associatedtype.Error" title="type serde::ser::SerializeMap::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;K: <a class="trait" href="../../serde/trait.Serialize.html" title="trait serde::Serialize">Serialize</a>,<br>&nbsp;&nbsp;&nbsp;&nbsp;V: <a class="trait" href="../../serde/trait.Serialize.html" title="trait serde::Serialize">Serialize</a>,&nbsp;</span></code></span></h3><div class='docblock'><p>Serialize a map entry consisting of a key and a value.</p>
<p>Some <a href="../trait.Serialize.html"><code>Serialize</code></a> types are not able to hold a key and value in memory
at the same time so <code>SerializeMap</code> implementations are required to
support <a href="#tymethod.serialize_key"><code>serialize_key</code></a> and <a href="#tymethod.serialize_value"><code>serialize_value</code></a> individually. The
<code>serialize_entry</code> method allows serializers to optimize for the case
where key and value are both available. <a href="../trait.Serialize.html"><code>Serialize</code></a> implementations
are encouraged to use <code>serialize_entry</code> if possible.</p>
<p>The default implementation delegates to <a href="#tymethod.serialize_key"><code>serialize_key</code></a> and
<a href="#tymethod.serialize_value"><code>serialize_value</code></a>. This is appropriate for serializers that do not
care about performance or are not able to optimize <code>serialize_entry</code> any
better than this.</p>
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Implementors<a href='#implementors' class='anchor'></a>
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<li><div class='out-of-band'><a class='srclink' href='../../src/serde/ser/impossible.rs.html#161-187' title='goto source code'>[src]</a></div><code>impl&lt;Ok, Error&gt; SerializeMap for <a class="struct" href="../../serde/ser/struct.Impossible.html" title="struct serde::ser::Impossible">Impossible</a>&lt;Ok, Error&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;Error: <a class="trait" href="../../serde/ser/trait.Error.html" title="trait serde::ser::Error">Error</a>,&nbsp;</span><span class="where fmt-newline"> type <a href='#associatedtype.Ok' class="type">Ok</a> = Ok;</span><span class="where fmt-newline"> type <a href='#associatedtype.Error' class="type">Error</a> = Error;</span></code></li>
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