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<p class='location'>Enum Option</p><div class="block items"><ul><li><a href="#variants">Variants</a></li><li><a href="#methods">Methods</a></li><li><a href="#implementations">Trait Implementations</a></li></ul></div><p class='location'><a href='../index.html'>core</a>::<wbr><a href='index.html'>option</a></p><script>window.sidebarCurrent = {name: 'Option', ty: 'enum', relpath: ''};</script><script defer src="sidebar-items.js"></script>
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<h1 class='fqn'><span class='in-band'>Enum <a href='../index.html'>core</a>::<wbr><a href='index.html'>option</a>::<wbr><a class="enum" href=''>Option</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><span id='render-detail'>
<a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">
[<span class='inner'>−</span>]
</a>
</span><a class='srclink' href='../../src/core/option.rs.html#159-166' title='goto source code'>[src]</a></span></h1>
<pre class='rust enum'>pub enum Option<T> {
None,
Some(T),
}</pre><div class='docblock'><p>The <code>Option</code> type. See <a href="index.html">the module level documentation</a> for more.</p>
</div><h2 id='variants' class='variants'>Variants</h2>
<span id='variant.None' class='variant'><span id='None.v' class='invisible'><code>None</code></span></span><div class='docblock'><p>No value</p>
</div><span id='variant.Some' class='variant'><span id='Some.v' class='invisible'><code>Some(T)</code></span></span><div class='docblock'><p>Some value <code>T</code></p>
</div><h2 id='methods'>Methods</h2><h3 class='impl'><span class='in-band'><code>impl<T> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#172-760' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.is_some' class="method"><span id='is_some.v' class='invisible'><code>fn <a href='#method.is_some' class='fnname'>is_some</a>(&self) -> bool</code></span></h4>
<div class='docblock'><p>Returns <code>true</code> if the option is a <a href="#variant.Some"><code>Some</code></a> value.</p>
<h1 id='examples' class='section-header'><a href='#examples'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">is_some</span>(), <span class="bool-val">true</span>);
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">is_some</span>(), <span class="bool-val">false</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20Some(2)%3B%0Aassert_eq!(x.is_some()%2C%20true)%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Aassert_eq!(x.is_some()%2C%20false)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.is_none' class="method"><span id='is_none.v' class='invisible'><code>fn <a href='#method.is_none' class='fnname'>is_none</a>(&self) -> bool</code></span></h4>
<div class='docblock'><p>Returns <code>true</code> if the option is a <a href="#variant.None"><code>None</code></a> value.</p>
<h1 id='examples-1' class='section-header'><a href='#examples-1'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">is_none</span>(), <span class="bool-val">false</span>);
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">is_none</span>(), <span class="bool-val">true</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20Some(2)%3B%0Aassert_eq!(x.is_none()%2C%20false)%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Aassert_eq!(x.is_none()%2C%20true)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.as_ref' class="method"><span id='as_ref.v' class='invisible'><code>fn <a href='#method.as_ref' class='fnname'>as_ref</a>(&self) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><&T></code></span></h4>
<div class='docblock'><p>Converts from <code>Option<T></code> to <code>Option<&T></code>.</p>
<h1 id='examples-2' class='section-header'><a href='#examples-2'>Examples</a></h1>
<p>Convert an <code>Option<</code><a href="../../std/string/struct.String.html"><code>String</code></a><code>></code> into an <code>Option<</code><a href="../../std/primitive.usize.html"><code>usize</code></a><code>></code>, preserving the original.
The <a href="enum.Option.html#method.map"><code>map</code></a> method takes the <code>self</code> argument by value, consuming the original,
so this technique uses <code>as_ref</code> to first take an <code>Option</code> to a reference
to the value inside the original.</p>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">num_as_str</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">String</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"10"</span>.<span class="ident">to_string</span>());
<span class="comment">// First, cast `Option<String>` to `Option<&String>` with `as_ref`,</span>
<span class="comment">// then consume *that* with `map`, leaving `num_as_str` on the stack.</span>
<span class="kw">let</span> <span class="ident">num_as_int</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span> <span class="op">=</span> <span class="ident">num_as_str</span>.<span class="ident">as_ref</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">n</span><span class="op">|</span> <span class="ident">n</span>.<span class="ident">len</span>());
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"still can print num_as_str: {:?}"</span>, <span class="ident">num_as_str</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20num_as_str%3A%20Option%3CString%3E%20%3D%20Some(%2210%22.to_string())%3B%0A%2F%2F%20First%2C%20cast%20%60Option%3CString%3E%60%20to%20%60Option%3C%26String%3E%60%20with%20%60as_ref%60%2C%0A%2F%2F%20then%20consume%20*that*%20with%20%60map%60%2C%20leaving%20%60num_as_str%60%20on%20the%20stack.%0Alet%20num_as_int%3A%20Option%3Cusize%3E%20%3D%20num_as_str.as_ref().map(%7Cn%7C%20n.len())%3B%0Aprintln!(%22still%20can%20print%20num_as_str%3A%20%7B%3A%3F%7D%22%2C%20num_as_str)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.as_mut' class="method"><span id='as_mut.v' class='invisible'><code>fn <a href='#method.as_mut' class='fnname'>as_mut</a>(&mut self) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><&mut T></code></span></h4>
<div class='docblock'><p>Converts from <code>Option<T></code> to <code>Option<&mut T></code>.</p>
<h1 id='examples-3' class='section-header'><a href='#examples-3'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">match</span> <span class="ident">x</span>.<span class="ident">as_mut</span>() {
<span class="prelude-val">Some</span>(<span class="ident">v</span>) <span class="op">=></span> <span class="kw-2">*</span><span class="ident">v</span> <span class="op">=</span> <span class="number">42</span>,
<span class="prelude-val">None</span> <span class="op">=></span> {},
}
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">Some</span>(<span class="number">42</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20mut%20x%20%3D%20Some(2)%3B%0Amatch%20x.as_mut()%20%7B%0A%20%20%20%20Some(v)%20%3D%3E%20*v%20%3D%2042%2C%0A%20%20%20%20None%20%3D%3E%20%7B%7D%2C%0A%7D%0Aassert_eq!(x%2C%20Some(42))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.expect' class="method"><span id='expect.v' class='invisible'><code>fn <a href='#method.expect' class='fnname'>expect</a>(self, msg: &str) -> T</code></span></h4>
<div class='docblock'><p>Unwraps an option, yielding the content of a <a href="#variant.Some"><code>Some</code></a>.</p>
<h1 id='panics' class='section-header'><a href='#panics'>Panics</a></h1>
<p>Panics if the value is a <a href="#variant.None"><code>None</code></a> with a custom panic message provided by
<code>msg</code>.</p>
<h1 id='examples-4' class='section-header'><a href='#examples-4'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"value"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">expect</span>(<span class="string">"the world is ending"</span>), <span class="string">"value"</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22value%22)%3B%0Aassert_eq!(x.expect(%22the%20world%20is%20ending%22)%2C%20%22value%22)%3B%0A%7D">Run</a></pre>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="ident">x</span>.<span class="ident">expect</span>(<span class="string">"the world is ending"</span>); <span class="comment">// panics with `the world is ending`</span><a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Ax.expect(%22the%20world%20is%20ending%22)%3B%20%2F%2F%20panics%20with%20%60the%20world%20is%20ending%60%0A%7D">Run</a></pre>
</div><h4 id='method.unwrap' class="method"><span id='unwrap.v' class='invisible'><code>fn <a href='#method.unwrap' class='fnname'>unwrap</a>(self) -> T</code></span></h4>
<div class='docblock'><p>Moves the value <code>v</code> out of the <code>Option<T></code> if it is <a href="#variant.Some"><code>Some(v)</code></a>.</p>
<p>In general, because this function may panic, its use is discouraged.
Instead, prefer to use pattern matching and handle the <a href="#variant.None"><code>None</code></a>
case explicitly.</p>
<h1 id='panics-1' class='section-header'><a href='#panics-1'>Panics</a></h1>
<p>Panics if the self value equals <a href="#variant.None"><code>None</code></a>.</p>
<h1 id='examples-5' class='section-header'><a href='#examples-5'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"air"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">unwrap</span>(), <span class="string">"air"</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22air%22)%3B%0Aassert_eq!(x.unwrap()%2C%20%22air%22)%3B%0A%7D">Run</a></pre>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">unwrap</span>(), <span class="string">"air"</span>); <span class="comment">// fails</span><a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.unwrap()%2C%20%22air%22)%3B%20%2F%2F%20fails%0A%7D">Run</a></pre>
</div><h4 id='method.unwrap_or' class="method"><span id='unwrap_or.v' class='invisible'><code>fn <a href='#method.unwrap_or' class='fnname'>unwrap_or</a>(self, def: T) -> T</code></span></h4>
<div class='docblock'><p>Returns the contained value or a default.</p>
<h1 id='examples-6' class='section-header'><a href='#examples-6'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="string">"car"</span>).<span class="ident">unwrap_or</span>(<span class="string">"bike"</span>), <span class="string">"car"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">None</span>.<span class="ident">unwrap_or</span>(<span class="string">"bike"</span>), <span class="string">"bike"</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Aassert_eq!(Some(%22car%22).unwrap_or(%22bike%22)%2C%20%22car%22)%3B%0Aassert_eq!(None.unwrap_or(%22bike%22)%2C%20%22bike%22)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.unwrap_or_else' class="method"><span id='unwrap_or_else.v' class='invisible'><code>fn <a href='#method.unwrap_or_else' class='fnname'>unwrap_or_else</a><F: <a class="trait" href="../../core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>() -> T>(self, f: F) -> T</code></span></h4>
<div class='docblock'><p>Returns the contained value or computes it from a closure.</p>
<h1 id='examples-7' class='section-header'><a href='#examples-7'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">k</span> <span class="op">=</span> <span class="number">10</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="number">4</span>).<span class="ident">unwrap_or_else</span>(<span class="op">||</span> <span class="number">2</span> <span class="op">*</span> <span class="ident">k</span>), <span class="number">4</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">None</span>.<span class="ident">unwrap_or_else</span>(<span class="op">||</span> <span class="number">2</span> <span class="op">*</span> <span class="ident">k</span>), <span class="number">20</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20k%20%3D%2010%3B%0Aassert_eq!(Some(4).unwrap_or_else(%7C%7C%202%20*%20k)%2C%204)%3B%0Aassert_eq!(None.unwrap_or_else(%7C%7C%202%20*%20k)%2C%2020)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.map' class="method"><span id='map.v' class='invisible'><code>fn <a href='#method.map' class='fnname'>map</a><U, F: <a class="trait" href="../../core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>(T) -> U>(self, f: F) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><U></code></span></h4>
<div class='docblock'><p>Maps an <code>Option<T></code> to <code>Option<U></code> by applying a function to a contained value.</p>
<h1 id='examples-8' class='section-header'><a href='#examples-8'>Examples</a></h1>
<p>Convert an <code>Option<</code><a href="../../std/string/struct.String.html"><code>String</code></a><code>></code> into an <code>Option<</code><a href="../../std/primitive.usize.html"><code>usize</code></a><code>></code>, consuming the original:</p>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">maybe_some_string</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">String</span>::<span class="ident">from</span>(<span class="string">"Hello, World!"</span>));
<span class="comment">// `Option::map` takes self *by value*, consuming `maybe_some_string`</span>
<span class="kw">let</span> <span class="ident">maybe_some_len</span> <span class="op">=</span> <span class="ident">maybe_some_string</span>.<span class="ident">map</span>(<span class="op">|</span><span class="ident">s</span><span class="op">|</span> <span class="ident">s</span>.<span class="ident">len</span>());
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">maybe_some_len</span>, <span class="prelude-val">Some</span>(<span class="number">13</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20maybe_some_string%20%3D%20Some(String%3A%3Afrom(%22Hello%2C%20World!%22))%3B%0A%2F%2F%20%60Option%3A%3Amap%60%20takes%20self%20*by%20value*%2C%20consuming%20%60maybe_some_string%60%0Alet%20maybe_some_len%20%3D%20maybe_some_string.map(%7Cs%7C%20s.len())%3B%0A%0Aassert_eq!(maybe_some_len%2C%20Some(13))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.map_or' class="method"><span id='map_or.v' class='invisible'><code>fn <a href='#method.map_or' class='fnname'>map_or</a><U, F: <a class="trait" href="../../core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>(T) -> U>(self, default: U, f: F) -> U</code></span></h4>
<div class='docblock'><p>Applies a function to the contained value (if any),
or returns a <a href="../default/trait.Default.html#tymethod.default"><code>default</code></a> (if not).</p>
<h1 id='examples-9' class='section-header'><a href='#examples-9'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">map_or</span>(<span class="number">42</span>, <span class="op">|</span><span class="ident">v</span><span class="op">|</span> <span class="ident">v</span>.<span class="ident">len</span>()), <span class="number">3</span>);
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">map_or</span>(<span class="number">42</span>, <span class="op">|</span><span class="ident">v</span><span class="op">|</span> <span class="ident">v</span>.<span class="ident">len</span>()), <span class="number">42</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.map_or(42%2C%20%7Cv%7C%20v.len())%2C%203)%3B%0A%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.map_or(42%2C%20%7Cv%7C%20v.len())%2C%2042)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.map_or_else' class="method"><span id='map_or_else.v' class='invisible'><code>fn <a href='#method.map_or_else' class='fnname'>map_or_else</a><U, D: <a class="trait" href="../../core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>() -> U, F: <a class="trait" href="../../core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>(T) -> U>(<br> self, <br> default: D, <br> f: F<br>) -> U</code></span></h4>
<div class='docblock'><p>Applies a function to the contained value (if any),
or computes a <a href="../default/trait.Default.html#tymethod.default"><code>default</code></a> (if not).</p>
<h1 id='examples-10' class='section-header'><a href='#examples-10'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">k</span> <span class="op">=</span> <span class="number">21</span>;
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">map_or_else</span>(<span class="op">||</span> <span class="number">2</span> <span class="op">*</span> <span class="ident">k</span>, <span class="op">|</span><span class="ident">v</span><span class="op">|</span> <span class="ident">v</span>.<span class="ident">len</span>()), <span class="number">3</span>);
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">map_or_else</span>(<span class="op">||</span> <span class="number">2</span> <span class="op">*</span> <span class="ident">k</span>, <span class="op">|</span><span class="ident">v</span><span class="op">|</span> <span class="ident">v</span>.<span class="ident">len</span>()), <span class="number">42</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20k%20%3D%2021%3B%0A%0Alet%20x%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.map_or_else(%7C%7C%202%20*%20k%2C%20%7Cv%7C%20v.len())%2C%203)%3B%0A%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.map_or_else(%7C%7C%202%20*%20k%2C%20%7Cv%7C%20v.len())%2C%2042)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.ok_or' class="method"><span id='ok_or.v' class='invisible'><code>fn <a href='#method.ok_or' class='fnname'>ok_or</a><E>(self, err: E) -> <a class="enum" href="../../core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, E></code></span></h4>
<div class='docblock'><p>Transforms the <code>Option<T></code> into a <a href="../../std/result/enum.Result.html"><code>Result<T, E></code></a>, mapping <a href="#variant.Some"><code>Some(v)</code></a> to
<a href="../../std/result/enum.Result.html#variant.Ok"><code>Ok(v)</code></a> and <a href="#variant.None"><code>None</code></a> to <a href="../../std/result/enum.Result.html#variant.Err"><code>Err(err)</code></a>.</p>
<h1 id='examples-11' class='section-header'><a href='#examples-11'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">ok_or</span>(<span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="string">"foo"</span>));
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">ok_or</span>(<span class="number">0</span>), <span class="prelude-val">Err</span>(<span class="number">0</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.ok_or(0)%2C%20Ok(%22foo%22))%3B%0A%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.ok_or(0)%2C%20Err(0))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.ok_or_else' class="method"><span id='ok_or_else.v' class='invisible'><code>fn <a href='#method.ok_or_else' class='fnname'>ok_or_else</a><E, F: <a class="trait" href="../../core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>() -> E>(self, err: F) -> <a class="enum" href="../../core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, E></code></span></h4>
<div class='docblock'><p>Transforms the <code>Option<T></code> into a <a href="../../std/result/enum.Result.html"><code>Result<T, E></code></a>, mapping <a href="#variant.Some"><code>Some(v)</code></a> to
<a href="../../std/result/enum.Result.html#variant.Ok"><code>Ok(v)</code></a> and <a href="#variant.None"><code>None</code></a> to <a href="../../std/result/enum.Result.html#variant.Err"><code>Err(err())</code></a>.</p>
<h1 id='examples-12' class='section-header'><a href='#examples-12'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">ok_or_else</span>(<span class="op">||</span> <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="string">"foo"</span>));
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">ok_or_else</span>(<span class="op">||</span> <span class="number">0</span>), <span class="prelude-val">Err</span>(<span class="number">0</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.ok_or_else(%7C%7C%200)%2C%20Ok(%22foo%22))%3B%0A%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.ok_or_else(%7C%7C%200)%2C%20Err(0))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.iter' class="method"><span id='iter.v' class='invisible'><code>fn <a href='#method.iter' class='fnname'>iter</a>(&self) -> <a class="struct" href="../../core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a><T></code></span></h4>
<div class='docblock'><p>Returns an iterator over the possibly contained value.</p>
<h1 id='examples-13' class='section-header'><a href='#examples-13'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">4</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">iter</span>().<span class="ident">next</span>(), <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="number">4</span>));
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">iter</span>().<span class="ident">next</span>(), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%20%3D%20Some(4)%3B%0Aassert_eq!(x.iter().next()%2C%20Some(%264))%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Aassert_eq!(x.iter().next()%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.iter_mut' class="method"><span id='iter_mut.v' class='invisible'><code>fn <a href='#method.iter_mut' class='fnname'>iter_mut</a>(&mut self) -> <a class="struct" href="../../core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a><T></code></span></h4>
<div class='docblock'><p>Returns a mutable iterator over the possibly contained value.</p>
<h1 id='examples-14' class='section-header'><a href='#examples-14'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">4</span>);
<span class="kw">match</span> <span class="ident">x</span>.<span class="ident">iter_mut</span>().<span class="ident">next</span>() {
<span class="prelude-val">Some</span>(<span class="ident">v</span>) <span class="op">=></span> <span class="kw-2">*</span><span class="ident">v</span> <span class="op">=</span> <span class="number">42</span>,
<span class="prelude-val">None</span> <span class="op">=></span> {},
}
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">Some</span>(<span class="number">42</span>));
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">iter_mut</span>().<span class="ident">next</span>(), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20mut%20x%20%3D%20Some(4)%3B%0Amatch%20x.iter_mut().next()%20%7B%0A%20%20%20%20Some(v)%20%3D%3E%20*v%20%3D%2042%2C%0A%20%20%20%20None%20%3D%3E%20%7B%7D%2C%0A%7D%0Aassert_eq!(x%2C%20Some(42))%3B%0A%0Alet%20mut%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Aassert_eq!(x.iter_mut().next()%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.and' class="method"><span id='and.v' class='invisible'><code>fn <a href='#method.and' class='fnname'>and</a><U>(self, optb: <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><U>) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><U></code></span></h4>
<div class='docblock'><p>Returns <a href="#variant.None"><code>None</code></a> if the option is <a href="#variant.None"><code>None</code></a>, otherwise returns <code>optb</code>.</p>
<h1 id='examples-15' class='section-header'><a href='#examples-15'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">and</span>(<span class="ident">y</span>), <span class="prelude-val">None</span>);
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">and</span>(<span class="ident">y</span>), <span class="prelude-val">None</span>);
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">and</span>(<span class="ident">y</span>), <span class="prelude-val">Some</span>(<span class="string">"foo"</span>));
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">and</span>(<span class="ident">y</span>), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%20%3D%20Some(2)%3B%0Alet%20y%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.and(y)%2C%20None)%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Alet%20y%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.and(y)%2C%20None)%3B%0A%0Alet%20x%20%3D%20Some(2)%3B%0Alet%20y%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.and(y)%2C%20Some(%22foo%22))%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Alet%20y%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.and(y)%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.and_then' class="method"><span id='and_then.v' class='invisible'><code>fn <a href='#method.and_then' class='fnname'>and_then</a><U, F: <a class="trait" href="../../core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>(T) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><U>>(self, f: F) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><U></code></span></h4>
<div class='docblock'><p>Returns <a href="#variant.None"><code>None</code></a> if the option is <a href="#variant.None"><code>None</code></a>, otherwise calls <code>f</code> with the
wrapped value and returns the result.</p>
<p>Some languages call this operation flatmap.</p>
<h1 id='examples-16' class='section-header'><a href='#examples-16'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">fn</span> <span class="ident">sq</span>(<span class="ident">x</span>: <span class="ident">u32</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> { <span class="prelude-val">Some</span>(<span class="ident">x</span> <span class="op">*</span> <span class="ident">x</span>) }
<span class="kw">fn</span> <span class="ident">nope</span>(_: <span class="ident">u32</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> { <span class="prelude-val">None</span> }
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="number">2</span>).<span class="ident">and_then</span>(<span class="ident">sq</span>).<span class="ident">and_then</span>(<span class="ident">sq</span>), <span class="prelude-val">Some</span>(<span class="number">16</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="number">2</span>).<span class="ident">and_then</span>(<span class="ident">sq</span>).<span class="ident">and_then</span>(<span class="ident">nope</span>), <span class="prelude-val">None</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="number">2</span>).<span class="ident">and_then</span>(<span class="ident">nope</span>).<span class="ident">and_then</span>(<span class="ident">sq</span>), <span class="prelude-val">None</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">None</span>.<span class="ident">and_then</span>(<span class="ident">sq</span>).<span class="ident">and_then</span>(<span class="ident">sq</span>), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Afn%20sq(x%3A%20u32)%20-%3E%20Option%3Cu32%3E%20%7B%20Some(x%20*%20x)%20%7D%0Afn%20nope(_%3A%20u32)%20-%3E%20Option%3Cu32%3E%20%7B%20None%20%7D%0A%0Aassert_eq!(Some(2).and_then(sq).and_then(sq)%2C%20Some(16))%3B%0Aassert_eq!(Some(2).and_then(sq).and_then(nope)%2C%20None)%3B%0Aassert_eq!(Some(2).and_then(nope).and_then(sq)%2C%20None)%3B%0Aassert_eq!(None.and_then(sq).and_then(sq)%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.or' class="method"><span id='or.v' class='invisible'><code>fn <a href='#method.or' class='fnname'>or</a>(self, optb: <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T>) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span></h4>
<div class='docblock'><p>Returns the option if it contains a value, otherwise returns <code>optb</code>.</p>
<h1 id='examples-17' class='section-header'><a href='#examples-17'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">or</span>(<span class="ident">y</span>), <span class="prelude-val">Some</span>(<span class="number">2</span>));
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">100</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">or</span>(<span class="ident">y</span>), <span class="prelude-val">Some</span>(<span class="number">100</span>));
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">100</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">or</span>(<span class="ident">y</span>), <span class="prelude-val">Some</span>(<span class="number">2</span>));
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">or</span>(<span class="ident">y</span>), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%20%3D%20Some(2)%3B%0Alet%20y%20%3D%20None%3B%0Aassert_eq!(x.or(y)%2C%20Some(2))%3B%0A%0Alet%20x%20%3D%20None%3B%0Alet%20y%20%3D%20Some(100)%3B%0Aassert_eq!(x.or(y)%2C%20Some(100))%3B%0A%0Alet%20x%20%3D%20Some(2)%3B%0Alet%20y%20%3D%20Some(100)%3B%0Aassert_eq!(x.or(y)%2C%20Some(2))%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Alet%20y%20%3D%20None%3B%0Aassert_eq!(x.or(y)%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.or_else' class="method"><span id='or_else.v' class='invisible'><code>fn <a href='#method.or_else' class='fnname'>or_else</a><F: <a class="trait" href="../../core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>() -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T>>(self, f: F) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span></h4>
<div class='docblock'><p>Returns the option if it contains a value, otherwise calls <code>f</code> and
returns the result.</p>
<h1 id='examples-18' class='section-header'><a href='#examples-18'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">fn</span> <span class="ident">nobody</span>() <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'static</span> <span class="ident">str</span><span class="op">></span> { <span class="prelude-val">None</span> }
<span class="kw">fn</span> <span class="ident">vikings</span>() <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'static</span> <span class="ident">str</span><span class="op">></span> { <span class="prelude-val">Some</span>(<span class="string">"vikings"</span>) }
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="string">"barbarians"</span>).<span class="ident">or_else</span>(<span class="ident">vikings</span>), <span class="prelude-val">Some</span>(<span class="string">"barbarians"</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">None</span>.<span class="ident">or_else</span>(<span class="ident">vikings</span>), <span class="prelude-val">Some</span>(<span class="string">"vikings"</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">None</span>.<span class="ident">or_else</span>(<span class="ident">nobody</span>), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Afn%20nobody()%20-%3E%20Option%3C%26'static%20str%3E%20%7B%20None%20%7D%0Afn%20vikings()%20-%3E%20Option%3C%26'static%20str%3E%20%7B%20Some(%22vikings%22)%20%7D%0A%0Aassert_eq!(Some(%22barbarians%22).or_else(vikings)%2C%20Some(%22barbarians%22))%3B%0Aassert_eq!(None.or_else(vikings)%2C%20Some(%22vikings%22))%3B%0Aassert_eq!(None.or_else(nobody)%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.get_or_insert' class="method"><span id='get_or_insert.v' class='invisible'><code>fn <a href='#method.get_or_insert' class='fnname'>get_or_insert</a>(&mut self, v: T) -> &mut T</code></span></h4>
<div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>option_entry </code><a href="https://github.com/rust-lang/rust/issues/39288">#39288</a>)</div></div><div class='docblock'><p>Inserts <code>v</code> into the option if it is <a href="#variant.None"><code>None</code></a>, then
returns a mutable reference to the contained value.</p>
<h1 id='examples-19' class='section-header'><a href='#examples-19'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="attribute">#<span class="op">!</span>[<span class="ident">feature</span>(<span class="ident">option_entry</span>)]</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">None</span>;
{
<span class="kw">let</span> <span class="ident">y</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">u32</span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">get_or_insert</span>(<span class="number">5</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">y</span>, <span class="kw-2">&</span><span class="number">5</span>);
<span class="kw-2">*</span><span class="ident">y</span> <span class="op">=</span> <span class="number">7</span>;
}
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">Some</span>(<span class="number">7</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Bfeature(option_entry)%5D%0A%0Afn%20main()%20%7B%0Alet%20mut%20x%20%3D%20None%3B%0A%0A%7B%0A%20%20%20%20let%20y%3A%20%26mut%20u32%20%3D%20x.get_or_insert(5)%3B%0A%20%20%20%20assert_eq!(y%2C%20%265)%3B%0A%0A%20%20%20%20*y%20%3D%207%3B%0A%7D%0A%0Aassert_eq!(x%2C%20Some(7))%3B%0A%7D&version=nightly">Run</a></pre>
</div><h4 id='method.get_or_insert_with' class="method"><span id='get_or_insert_with.v' class='invisible'><code>fn <a href='#method.get_or_insert_with' class='fnname'>get_or_insert_with</a><F: <a class="trait" href="../../core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>() -> T>(&mut self, f: F) -> &mut T</code></span></h4>
<div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>option_entry </code><a href="https://github.com/rust-lang/rust/issues/39288">#39288</a>)</div></div><div class='docblock'><p>Inserts a value computed from <code>f</code> into the option if it is <a href="#variant.None"><code>None</code></a>, then
returns a mutable reference to the contained value.</p>
<h1 id='examples-20' class='section-header'><a href='#examples-20'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="attribute">#<span class="op">!</span>[<span class="ident">feature</span>(<span class="ident">option_entry</span>)]</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">None</span>;
{
<span class="kw">let</span> <span class="ident">y</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">u32</span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">get_or_insert_with</span>(<span class="op">||</span> <span class="number">5</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">y</span>, <span class="kw-2">&</span><span class="number">5</span>);
<span class="kw-2">*</span><span class="ident">y</span> <span class="op">=</span> <span class="number">7</span>;
}
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">Some</span>(<span class="number">7</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Bfeature(option_entry)%5D%0A%0Afn%20main()%20%7B%0Alet%20mut%20x%20%3D%20None%3B%0A%0A%7B%0A%20%20%20%20let%20y%3A%20%26mut%20u32%20%3D%20x.get_or_insert_with(%7C%7C%205)%3B%0A%20%20%20%20assert_eq!(y%2C%20%265)%3B%0A%0A%20%20%20%20*y%20%3D%207%3B%0A%7D%0A%0Aassert_eq!(x%2C%20Some(7))%3B%0A%7D&version=nightly">Run</a></pre>
</div><h4 id='method.take' class="method"><span id='take.v' class='invisible'><code>fn <a href='#method.take' class='fnname'>take</a>(&mut self) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span></h4>
<div class='docblock'><p>Takes the value out of the option, leaving a <a href="#variant.None"><code>None</code></a> in its place.</p>
<h1 id='examples-21' class='section-header'><a href='#examples-21'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="ident">x</span>.<span class="ident">take</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">None</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="ident">x</span>.<span class="ident">take</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20mut%20x%20%3D%20Some(2)%3B%0Ax.take()%3B%0Aassert_eq!(x%2C%20None)%3B%0A%0Alet%20mut%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Ax.take()%3B%0Aassert_eq!(x%2C%20None)%3B%0A%7D">Run</a></pre>
</div></div><h3 class='impl'><span class='in-band'><code>impl<'a, T: <a class="trait" href="../../core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a>> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><&'a T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#762-779' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.cloned' class="method"><span id='cloned.v' class='invisible'><code>fn <a href='#method.cloned' class='fnname'>cloned</a>(self) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span></h4>
<div class='docblock'><p>Maps an <code>Option<&T></code> to an <code>Option<T></code> by cloning the contents of the
option.</p>
<h1 id='examples-22' class='section-header'><a href='#examples-22'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="number">12</span>;
<span class="kw">let</span> <span class="ident">opt_x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="ident">x</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">opt_x</span>, <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="number">12</span>));
<span class="kw">let</span> <span class="ident">cloned</span> <span class="op">=</span> <span class="ident">opt_x</span>.<span class="ident">cloned</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cloned</span>, <span class="prelude-val">Some</span>(<span class="number">12</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%20%3D%2012%3B%0Alet%20opt_x%20%3D%20Some(%26x)%3B%0Aassert_eq!(opt_x%2C%20Some(%2612))%3B%0Alet%20cloned%20%3D%20opt_x.cloned()%3B%0Aassert_eq!(cloned%2C%20Some(12))%3B%0A%7D">Run</a></pre>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T: <a class="trait" href="../../core/default/trait.Default.html" title="trait core::default::Default">Default</a>> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#781-817' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.unwrap_or_default' class="method"><span id='unwrap_or_default.v' class='invisible'><code>fn <a href='#method.unwrap_or_default' class='fnname'>unwrap_or_default</a>(self) -> T</code></span></h4>
<div class='docblock'><p>Returns the contained value or a default</p>
<p>Consumes the <code>self</code> argument then, if <a href="#variant.Some"><code>Some</code></a>, returns the contained
value, otherwise if <a href="#variant.None"><code>None</code></a>, returns the default value for that
type.</p>
<h1 id='examples-23' class='section-header'><a href='#examples-23'>Examples</a></h1>
<p>Convert a string to an integer, turning poorly-formed strings
into 0 (the default value for integers). <a href="../../std/primitive.str.html#method.parse"><code>parse</code></a> converts
a string to any other type that implements <a href="../../std/str/trait.FromStr.html"><code>FromStr</code></a>, returning
<a href="#variant.None"><code>None</code></a> on error.</p>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">good_year_from_input</span> <span class="op">=</span> <span class="string">"1909"</span>;
<span class="kw">let</span> <span class="ident">bad_year_from_input</span> <span class="op">=</span> <span class="string">"190blarg"</span>;
<span class="kw">let</span> <span class="ident">good_year</span> <span class="op">=</span> <span class="ident">good_year_from_input</span>.<span class="ident">parse</span>().<span class="ident">ok</span>().<span class="ident">unwrap_or_default</span>();
<span class="kw">let</span> <span class="ident">bad_year</span> <span class="op">=</span> <span class="ident">bad_year_from_input</span>.<span class="ident">parse</span>().<span class="ident">ok</span>().<span class="ident">unwrap_or_default</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">1909</span>, <span class="ident">good_year</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0</span>, <span class="ident">bad_year</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20good_year_from_input%20%3D%20%221909%22%3B%0Alet%20bad_year_from_input%20%3D%20%22190blarg%22%3B%0Alet%20good_year%20%3D%20good_year_from_input.parse().ok().unwrap_or_default()%3B%0Alet%20bad_year%20%3D%20bad_year_from_input.parse().ok().unwrap_or_default()%3B%0A%0Aassert_eq!(1909%2C%20good_year)%3B%0Aassert_eq!(0%2C%20bad_year)%3B%0A%7D">Run</a></pre>
</div></div><h2 id='implementations'>Trait Implementations</h2><h3 class='impl'><span class='in-band'><code>impl<T: <a class="trait" href="../../core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a>> <a class="trait" href="../../core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.clone' class="method"><span id='clone.v' class='invisible'><code>fn <a href='../../core/clone/trait.Clone.html#tymethod.clone' class='fnname'>clone</a>(&self) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span></h4>
<div class='docblock'><p>Returns a copy of the value. <a href="../../core/clone/trait.Clone.html#tymethod.clone">Read more</a></p>
</div><h4 id='method.clone_from' class="method"><span id='clone_from.v' class='invisible'><code>fn <a href='../../core/clone/trait.Clone.html#method.clone_from' class='fnname'>clone_from</a>(&mut self, source: &Self)</code></span></h4>
<div class='docblock'><p>Performs copy-assignment from <code>source</code>. <a href="../../core/clone/trait.Clone.html#method.clone_from">Read more</a></p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T: <a class="trait" href="../../core/marker/trait.Copy.html" title="trait core::marker::Copy">Copy</a>> <a class="trait" href="../../core/marker/trait.Copy.html" title="trait core::marker::Copy">Copy</a> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'></div><h3 class='impl'><span class='in-band'><code>impl<T: <a class="trait" href="../../core/cmp/trait.PartialEq.html" title="trait core::cmp::PartialEq">PartialEq</a>> <a class="trait" href="../../core/cmp/trait.PartialEq.html" title="trait core::cmp::PartialEq">PartialEq</a> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.eq' class="method"><span id='eq.v' class='invisible'><code>fn <a href='../../core/cmp/trait.PartialEq.html#tymethod.eq' class='fnname'>eq</a>(&self, __arg_0: &<a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T>) -> bool</code></span></h4>
<div class='docblock'><p>This method tests for <code>self</code> and <code>other</code> values to be equal, and is used by <code>==</code>. <a href="../../core/cmp/trait.PartialEq.html#tymethod.eq">Read more</a></p>
</div><h4 id='method.ne' class="method"><span id='ne.v' class='invisible'><code>fn <a href='../../core/cmp/trait.PartialEq.html#method.ne' class='fnname'>ne</a>(&self, __arg_0: &<a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T>) -> bool</code></span></h4>
<div class='docblock'><p>This method tests for <code>!=</code>.</p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T: <a class="trait" href="../../core/cmp/trait.PartialOrd.html" title="trait core::cmp::PartialOrd">PartialOrd</a>> <a class="trait" href="../../core/cmp/trait.PartialOrd.html" title="trait core::cmp::PartialOrd">PartialOrd</a> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.partial_cmp' class="method"><span id='partial_cmp.v' class='invisible'><code>fn <a href='../../core/cmp/trait.PartialOrd.html#tymethod.partial_cmp' class='fnname'>partial_cmp</a>(&self, __arg_0: &<a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T>) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><<a class="enum" href="../../core/cmp/enum.Ordering.html" title="enum core::cmp::Ordering">Ordering</a>></code></span></h4>
<div class='docblock'><p>This method returns an ordering between <code>self</code> and <code>other</code> values if one exists. <a href="../../core/cmp/trait.PartialOrd.html#tymethod.partial_cmp">Read more</a></p>
</div><h4 id='method.lt' class="method"><span id='lt.v' class='invisible'><code>fn <a href='../../core/cmp/trait.PartialOrd.html#method.lt' class='fnname'>lt</a>(&self, __arg_0: &<a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T>) -> bool</code></span></h4>
<div class='docblock'><p>This method tests less than (for <code>self</code> and <code>other</code>) and is used by the <code><</code> operator. <a href="../../core/cmp/trait.PartialOrd.html#method.lt">Read more</a></p>
</div><h4 id='method.le' class="method"><span id='le.v' class='invisible'><code>fn <a href='../../core/cmp/trait.PartialOrd.html#method.le' class='fnname'>le</a>(&self, __arg_0: &<a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T>) -> bool</code></span></h4>
<div class='docblock'><p>This method tests less than or equal to (for <code>self</code> and <code>other</code>) and is used by the <code><=</code> operator. <a href="../../core/cmp/trait.PartialOrd.html#method.le">Read more</a></p>
</div><h4 id='method.gt' class="method"><span id='gt.v' class='invisible'><code>fn <a href='../../core/cmp/trait.PartialOrd.html#method.gt' class='fnname'>gt</a>(&self, __arg_0: &<a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T>) -> bool</code></span></h4>
<div class='docblock'><p>This method tests greater than (for <code>self</code> and <code>other</code>) and is used by the <code>></code> operator. <a href="../../core/cmp/trait.PartialOrd.html#method.gt">Read more</a></p>
</div><h4 id='method.ge' class="method"><span id='ge.v' class='invisible'><code>fn <a href='../../core/cmp/trait.PartialOrd.html#method.ge' class='fnname'>ge</a>(&self, __arg_0: &<a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T>) -> bool</code></span></h4>
<div class='docblock'><p>This method tests greater than or equal to (for <code>self</code> and <code>other</code>) and is used by the <code>>=</code> operator. <a href="../../core/cmp/trait.PartialOrd.html#method.ge">Read more</a></p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T: <a class="trait" href="../../core/cmp/trait.Eq.html" title="trait core::cmp::Eq">Eq</a>> <a class="trait" href="../../core/cmp/trait.Eq.html" title="trait core::cmp::Eq">Eq</a> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'></div><h3 class='impl'><span class='in-band'><code>impl<T: <a class="trait" href="../../core/cmp/trait.Ord.html" title="trait core::cmp::Ord">Ord</a>> <a class="trait" href="../../core/cmp/trait.Ord.html" title="trait core::cmp::Ord">Ord</a> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.cmp' class="method"><span id='cmp.v' class='invisible'><code>fn <a href='../../core/cmp/trait.Ord.html#tymethod.cmp' class='fnname'>cmp</a>(&self, __arg_0: &<a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T>) -> <a class="enum" href="../../core/cmp/enum.Ordering.html" title="enum core::cmp::Ordering">Ordering</a></code></span></h4>
<div class='docblock'><p>This method returns an <code>Ordering</code> between <code>self</code> and <code>other</code>. <a href="../../core/cmp/trait.Ord.html#tymethod.cmp">Read more</a></p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T: <a class="trait" href="../../core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a>> <a class="trait" href="../../core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.fmt' class="method"><span id='fmt.v' class='invisible'><code>fn <a href='../../core/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, __arg_0: &mut <a class="struct" href="../../core/fmt/struct.Formatter.html" title="struct core::fmt::Formatter">Formatter</a>) -> <a class="type" href="../../core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></code></span></h4>
<div class='docblock'><p>Formats the value using the given formatter.</p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T: <a class="trait" href="../../core/hash/trait.Hash.html" title="trait core::hash::Hash">Hash</a>> <a class="trait" href="../../core/hash/trait.Hash.html" title="trait core::hash::Hash">Hash</a> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.hash' class="method"><span id='hash.v' class='invisible'><code>fn <a href='../../core/hash/trait.Hash.html#tymethod.hash' class='fnname'>hash</a><__HT: <a class="trait" href="../../core/hash/trait.Hasher.html" title="trait core::hash::Hasher">Hasher</a>>(&self, __arg_0: &mut __HT)</code></span></h4>
<div class='docblock'><p>Feeds this value into the given [<code>Hasher</code>]. <a href="../../core/hash/trait.Hash.html#tymethod.hash">Read more</a></p>
</div><h4 id='method.hash_slice' class="method"><span id='hash_slice.v' class='invisible'><code>fn <a href='../../core/hash/trait.Hash.html#method.hash_slice' class='fnname'>hash_slice</a><H: <a class="trait" href="../../core/hash/trait.Hasher.html" title="trait core::hash::Hasher">Hasher</a>>(data: &[Self], state: &mut H) <span class="where fmt-newline">where<br> Self: <a class="trait" href="../../core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></code><div class='since' title='Stable since Rust version 1.3.0'>1.3.0</div></span></h4>
<div class='docblock'><p>Feeds a slice of this type into the given [<code>Hasher</code>]. <a href="../../core/hash/trait.Hash.html#method.hash_slice">Read more</a></p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="../../core/default/trait.Default.html" title="trait core::default::Default">Default</a> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#832-838' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.default' class="method"><span id='default.v' class='invisible'><code>fn <a href='../../core/default/trait.Default.html#tymethod.default' class='fnname'>default</a>() -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span></h4>
<div class='docblock'><p>Returns <a href="#variant.None"><code>None</code></a>.</p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="../../core/iter/trait.IntoIterator.html" title="trait core::iter::IntoIterator">IntoIterator</a> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#841-862' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='associatedtype.Item' class="type"><span id='Item.t' class='invisible'><code>type <a href='../../core/iter/trait.IntoIterator.html#associatedtype.Item' class="type">Item</a> = T</code></span></h4>
<div class='docblock'><p>The type of the elements being iterated over.</p>
</div><h4 id='associatedtype.IntoIter' class="type"><span id='IntoIter.t' class='invisible'><code>type <a href='../../core/iter/trait.IntoIterator.html#associatedtype.IntoIter' class="type">IntoIter</a> = <a class="struct" href="../../core/option/struct.IntoIter.html" title="struct core::option::IntoIter">IntoIter</a><T></code></span></h4>
<div class='docblock'><p>Which kind of iterator are we turning this into?</p>
</div><h4 id='method.into_iter' class="method"><span id='into_iter.v' class='invisible'><code>fn <a href='../../core/iter/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -> <a class="struct" href="../../core/option/struct.IntoIter.html" title="struct core::option::IntoIter">IntoIter</a><T></code></span></h4>
<div class='docblock'><p>Returns a consuming iterator over the possibly contained value.</p>
<h1 id='examples-24' class='section-header'><a href='#examples-24'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"string"</span>);
<span class="kw">let</span> <span class="ident">v</span>: <span class="ident">Vec</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">into_iter</span>().<span class="ident">collect</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">v</span>, [<span class="string">"string"</span>]);
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">v</span>: <span class="ident">Vec</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">into_iter</span>().<span class="ident">collect</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">v</span>.<span class="ident">is_empty</span>());<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22string%22)%3B%0Alet%20v%3A%20Vec%3C%26str%3E%20%3D%20x.into_iter().collect()%3B%0Aassert_eq!(v%2C%20%5B%22string%22%5D)%3B%0A%0Alet%20x%20%3D%20None%3B%0Alet%20v%3A%20Vec%3C%26str%3E%20%3D%20x.into_iter().collect()%3B%0Aassert!(v.is_empty())%3B%0A%7D">Run</a></pre>
</div></div><h3 class='impl'><span class='in-band'><code>impl<'a, T> <a class="trait" href="../../core/iter/trait.IntoIterator.html" title="trait core::iter::IntoIterator">IntoIterator</a> for &'a <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.4.0'>1.4.0</div><a class='srclink' href='../../src/core/option.rs.html#865-872' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='associatedtype.Item-1' class="type"><span id='Item.t-1' class='invisible'><code>type <a href='../../core/iter/trait.IntoIterator.html#associatedtype.Item' class="type">Item</a> = &'a T</code></span></h4>
<div class='docblock'><p>The type of the elements being iterated over.</p>
</div><h4 id='associatedtype.IntoIter-1' class="type"><span id='IntoIter.t-1' class='invisible'><code>type <a href='../../core/iter/trait.IntoIterator.html#associatedtype.IntoIter' class="type">IntoIter</a> = <a class="struct" href="../../core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a><'a, T></code></span></h4>
<div class='docblock'><p>Which kind of iterator are we turning this into?</p>
</div><h4 id='method.into_iter-1' class="method"><span id='into_iter.v-1' class='invisible'><code>fn <a href='../../core/iter/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -> <a class="struct" href="../../core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a><'a, T></code></span></h4>
<div class='docblock'><p>Creates an iterator from a value. <a href="../../core/iter/trait.IntoIterator.html#tymethod.into_iter">Read more</a></p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<'a, T> <a class="trait" href="../../core/iter/trait.IntoIterator.html" title="trait core::iter::IntoIterator">IntoIterator</a> for &'a mut <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.4.0'>1.4.0</div><a class='srclink' href='../../src/core/option.rs.html#875-882' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='associatedtype.Item-2' class="type"><span id='Item.t-2' class='invisible'><code>type <a href='../../core/iter/trait.IntoIterator.html#associatedtype.Item' class="type">Item</a> = &'a mut T</code></span></h4>
<div class='docblock'><p>The type of the elements being iterated over.</p>
</div><h4 id='associatedtype.IntoIter-2' class="type"><span id='IntoIter.t-2' class='invisible'><code>type <a href='../../core/iter/trait.IntoIterator.html#associatedtype.IntoIter' class="type">IntoIter</a> = <a class="struct" href="../../core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a><'a, T></code></span></h4>
<div class='docblock'><p>Which kind of iterator are we turning this into?</p>
</div><h4 id='method.into_iter-2' class="method"><span id='into_iter.v-2' class='invisible'><code>fn <a href='../../core/iter/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -> <a class="struct" href="../../core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a><'a, T></code></span></h4>
<div class='docblock'><p>Creates an iterator from a value. <a href="../../core/iter/trait.IntoIterator.html#tymethod.into_iter">Read more</a></p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="../../core/convert/trait.From.html" title="trait core::convert::From">From</a><T> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.12.0'>1.12.0</div><a class='srclink' href='../../src/core/option.rs.html#885-889' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.from' class="method"><span id='from.v' class='invisible'><code>fn <a href='../../core/convert/trait.From.html#tymethod.from' class='fnname'>from</a>(val: T) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></code></span></h4>
<div class='docblock'><p>Performs the conversion.</p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<A, V: <a class="trait" href="../../core/iter/trait.FromIterator.html" title="trait core::iter::FromIterator">FromIterator</a><A>> <a class="trait" href="../../core/iter/trait.FromIterator.html" title="trait core::iter::FromIterator">FromIterator</a><<a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><A>> for <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><V></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#1053-1109' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.from_iter' class="method"><span id='from_iter.v' class='invisible'><code>fn <a href='../../core/iter/trait.FromIterator.html#tymethod.from_iter' class='fnname'>from_iter</a><I: <a class="trait" href="../../core/iter/trait.IntoIterator.html" title="trait core::iter::IntoIterator">IntoIterator</a><Item = <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><A>>>(iter: I) -> <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a><V></code></span></h4>
<div class='docblock'><p>Takes each element in the <a href="../iter/trait.Iterator.html"><code>Iterator</code></a>: if it is <a href="enum.Option.html#variant.None"><code>None</code></a>, no further
elements are taken, and the <a href="enum.Option.html#variant.None"><code>None</code></a> is returned. Should no <a href="enum.Option.html#variant.None"><code>None</code></a> occur, a
container with the values of each <code>Option</code> is returned.</p>
<p>Here is an example which increments every integer in a vector,
checking for overflow:</p>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">u16</span>;
<span class="kw">let</span> <span class="ident">v</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="number">1</span>, <span class="number">2</span>];
<span class="kw">let</span> <span class="ident">res</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">u16</span><span class="op">>></span> <span class="op">=</span> <span class="ident">v</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="op">|</span><span class="kw-2">&</span><span class="ident">x</span>: <span class="kw-2">&</span><span class="ident">u16</span><span class="op">|</span>
<span class="kw">if</span> <span class="ident">x</span> <span class="op">==</span> <span class="ident">u16</span>::<span class="ident">MAX</span> { <span class="prelude-val">None</span> }
<span class="kw">else</span> { <span class="prelude-val">Some</span>(<span class="ident">x</span> <span class="op">+</span> <span class="number">1</span>) }
).<span class="ident">collect</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">res</span> <span class="op">==</span> <span class="prelude-val">Some</span>(<span class="macro">vec</span><span class="macro">!</span>[<span class="number">2</span>, <span class="number">3</span>]));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Ause%20std%3A%3Au16%3B%0A%0Alet%20v%20%3D%20vec!%5B1%2C%202%5D%3B%0Alet%20res%3A%20Option%3CVec%3Cu16%3E%3E%20%3D%20v.iter().map(%7C%26x%3A%20%26u16%7C%0A%20%20%20%20if%20x%20%3D%3D%20u16%3A%3AMAX%20%7B%20None%20%7D%0A%20%20%20%20else%20%7B%20Some(x%20%2B%201)%20%7D%0A).collect()%3B%0Aassert!(res%20%3D%3D%20Some(vec!%5B2%2C%203%5D))%3B%0A%7D">Run</a></pre>
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