<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="API documentation for the Rust `Into` trait in crate `core`."><meta name="keywords" content="rust, rustlang, rust-lang, Into"><title>core::convert::Into - Rust</title><link rel="stylesheet" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../dark.css"><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><script src="../../storage.js"></script><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc trait"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../core/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a><p class='location'>Trait Into</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#required-methods">Required Methods</a><div class="sidebar-links"><a href="#tymethod.into">into</a></div><a class="sidebar-title" href="#implementors">Implementors</a></div><p class='location'><a href='../index.html'>core</a>::<wbr><a href='index.html'>convert</a></p><script>window.sidebarCurrent = {name: 'Into', ty: 'trait', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../../settings.html"><img src="../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='in-band'>Trait <a href='../index.html'>core</a>::<wbr><a href='index.html'>convert</a>::<wbr><a class="trait" href=''>Into</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/convert.rs.html#225-229' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class='rust trait'>pub trait Into<T>: <a class="trait" href="../../core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a> {
fn <a href='#tymethod.into' class='fnname'>into</a>(self) -> T;
}</pre></div><div class='docblock'><p>A conversion that consumes <code>self</code>, which may or may not be expensive. The
reciprocal of <a href="trait.From.html"><code>From</code></a>.</p>
<p><strong>Note: this trait must not fail</strong>. If the conversion can fail, use
<a href="trait.TryInto.html"><code>TryInto</code></a> or a dedicated method which returns an <a href="../../std/option/enum.Option.html"><code>Option<T></code></a> or a
<a href="../../std/result/enum.Result.html"><code>Result<T, E></code></a>.</p>
<p>Library authors should not directly implement this trait, but should prefer
implementing the <a href="trait.From.html"><code>From</code></a> trait, which offers greater flexibility and
provides an equivalent <code>Into</code> implementation for free, thanks to a blanket
implementation in the standard library.</p>
<h1 id="generic-implementations" class="section-header"><a href="#generic-implementations">Generic Implementations</a></h1>
<ul>
<li><a href="trait.From.html"><code>From<T></code></a><code>for U</code> implies <code>Into<U> for T</code></li>
<li><a href="trait.Into.html#tymethod.into"><code>into</code></a> is reflexive, which means that <code>Into<T> for T</code> is implemented</li>
</ul>
<h1 id="implementing-into" class="section-header"><a href="#implementing-into">Implementing <code>Into</code></a></h1>
<p>There is one exception to implementing <code>Into</code>, and it's kind of esoteric.
If the destination type is not part of the current crate, and it uses a
generic variable, then you can't implement <code>From</code> directly. For example,
take this crate:</p>
<div class='information'><div class='tooltip compile_fail'>ⓘ<span class='tooltiptext'>This example deliberately fails to compile</span></div></div><pre class="rust rust-example-rendered compile_fail">
<span class="kw">struct</span> <span class="ident">Wrapper</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>);
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">From</span><span class="op"><</span><span class="ident">Wrapper</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span> <span class="kw">for</span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">from</span>(<span class="ident">w</span>: <span class="ident">Wrapper</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">w</span>.<span class="number">0</span>
}
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Astruct%20Wrapper%3CT%3E(Vec%3CT%3E)%3B%0Aimpl%3CT%3E%20From%3CWrapper%3CT%3E%3E%20for%20Vec%3CT%3E%20%7B%0A%20%20%20%20fn%20from(w%3A%20Wrapper%3CT%3E)%20-%3E%20Vec%3CT%3E%20%7B%0A%20%20%20%20%20%20%20%20w.0%0A%20%20%20%20%7D%0A%7D%0A%7D">Run</a></pre>
<p>To fix this, you can implement <code>Into</code> directly:</p>
<pre class="rust rust-example-rendered">
<span class="kw">struct</span> <span class="ident">Wrapper</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>);
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Into</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span> <span class="kw">for</span> <span class="ident">Wrapper</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">into</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="self">self</span>.<span class="number">0</span>
}
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Astruct%20Wrapper%3CT%3E(Vec%3CT%3E)%3B%0Aimpl%3CT%3E%20Into%3CVec%3CT%3E%3E%20for%20Wrapper%3CT%3E%20%7B%0A%20%20%20%20fn%20into(self)%20-%3E%20Vec%3CT%3E%20%7B%0A%20%20%20%20%20%20%20%20self.0%0A%20%20%20%20%7D%0A%7D%0A%7D">Run</a></pre>
<p>This won't always allow the conversion: for example, <code>try!</code> and <code>?</code>
always use <code>From</code>. However, in most cases, people use <code>Into</code> to do the
conversions, and this will allow that.</p>
<p>In almost all cases, you should try to implement <code>From</code>, then fall back
to <code>Into</code> if <code>From</code> can't be implemented.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<p><a href="../../std/string/struct.String.html"><code>String</code></a> implements <code>Into<Vec<u8>></code>:</p>
<pre class="rust rust-example-rendered">
<span class="kw">fn</span> <span class="ident">is_hello</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Into</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">>></span><span class="op">></span>(<span class="ident">s</span>: <span class="ident">T</span>) {
<span class="kw">let</span> <span class="ident">bytes</span> <span class="op">=</span> <span class="string">b"hello"</span>.<span class="ident">to_vec</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">bytes</span>, <span class="ident">s</span>.<span class="ident">into</span>());
}
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="string">"hello"</span>.<span class="ident">to_string</span>();
<span class="ident">is_hello</span>(<span class="ident">s</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Afn%20is_hello%3CT%3A%20Into%3CVec%3Cu8%3E%3E%3E(s%3A%20T)%20%7B%0A%20%20%20let%20bytes%20%3D%20b%22hello%22.to_vec()%3B%0A%20%20%20assert_eq!(bytes%2C%20s.into())%3B%0A%7D%0A%0Alet%20s%20%3D%20%22hello%22.to_string()%3B%0Ais_hello(s)%3B%0A%7D">Run</a></pre>
</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.into' class='method'><span id='into.v' class='invisible'><code>fn <a href='#tymethod.into' class='fnname'>into</a>(self) -> T</code></span></h3><div class='docblock'><p>Performs the conversion.</p>
</div></div>
<h2 id='implementors' class='small-section-header'>
Implementors<a href='#implementors' class='anchor'></a>
</h2>
<ul class='item-list' id='implementors-list'>
<li><table class='table-display'><tbody><tr><td><code>impl<T, U> Into<U> for T <span class="where fmt-newline">where<br> U: <a class="trait" href="../../core/convert/trait.From.html" title="trait core::convert::From">From</a><T>, </span></code><td><div class='out-of-band'><a class='srclink' href='../../src/core/convert.rs.html#393-398' title='goto source code'>[src]</a></div></td></tr></tbody></table></li>
</ul><script type="text/javascript">window.inlined_types=new Set([]);</script><script type="text/javascript" async
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