<!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"> <title>Deref coercions</title> <link rel="stylesheet" type="text/css" href="../rust.css"> <link rel="shortcut icon" href="https://www.rust-lang.org/favicon.ico"> </head> <body class="rustdoc"> <!--[if lte IE 8]> <div class="warning"> This old browser is unsupported and will most likely display funky things. </div> <![endif]--> <div id="versioninfo"> <img src="https://www.rust-lang.org/logos/rust-logo-32x32-blk.png" width="32" height="32" alt="Rust logo"><br> <span class="white-sticker"><a href="https://www.rust-lang.org">Rust</a> 1.27.1</span><br> <a href="https://github.com/rust-lang/rust/commit/" class="hash white-sticker"></a> </div> <h1 class="title">Deref coercions</h1> <p><small>There is a new edition of the book and this is an old link.</small></p> <blockquote> <p>Implementing the <code>Deref</code> trait allows us to customize the behavior of the <em>dereference operator</em> <code>*</code>. By implementing <code>Deref</code> in such a way that a smart pointer can be treated like a regular reference, we can write code that operates on references and use that code with smart pointers too.</p> </blockquote> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">ops</span>::<span class="ident">Deref</span>; <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Deref</span> <span class="kw">for</span> <span class="ident">MyBox</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="kw">type</span> <span class="ident">Target</span> <span class="op">=</span> <span class="ident">T</span>; <span class="kw">fn</span> <span class="ident">deref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">T</span> { <span class="kw-2">&</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%0Ause%20std%3A%3Aops%3A%3ADeref%3B%0A%0Astruct%20MyBox%3CT%3E(T)%3B%0Aimpl%3CT%3E%20Deref%20for%20MyBox%3CT%3E%20%7B%0A%20%20%20%20type%20Target%20%3D%20T%3B%0A%0A%20%20%20%20fn%20deref(%26self)%20-%3E%20%26T%20%7B%0A%20%20%20%20%20%20%20%20%26self.0%0A%20%20%20%20%7D%0A%7D%0A%7D">Run</a></pre> <hr /> <p>Here are the relevant sections in the new and old books:</p> <ul> <li><strong><a href="second-edition/ch15-02-deref.html">In the second edition: Ch 15.02 — Treating Smart Pointers like Regular References with the <code>Deref</code> Trait</a></strong></li> <li><small><a href="first-edition/deref-coercions.html">In the first edition: Ch 3.33 — Deref coercions</a></small></li> </ul> <footer><p> Copyright © 2011 The Rust Project Developers. Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a> or the <a href="https://opensource.org/licenses/MIT">MIT license</a>, at your option. </p><p> This file may not be copied, modified, or distributed except according to those terms. </p></footer> </body> </html>