<!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 `Ref` struct in crate `std`."> <meta name="keywords" content="rust, rustlang, rust-lang, Ref"> <title>std::cell::Ref - 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="../../main.css" id="themeStyle"> <script src="../../storage.js"></script> <link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"> </head> <body class="rustdoc struct"> <!--[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='../../std/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a> <p class='location'>Struct Ref</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#methods">Methods</a><div class="sidebar-links"><a href="#method.clone">clone</a><a href="#method.map">map</a></div><a class="sidebar-title" href="#implementations">Trait Implementations</a><div class="sidebar-links"><a href="#impl-Debug">Debug</a><a href="#impl-CoerceUnsized%3CRef%3C%27b%2C%20U%3E%3E">CoerceUnsized<Ref<'b, U>></a><a href="#impl-Deref">Deref</a><a href="#impl-Display">Display</a></div></div><p class='location'><a href='../index.html'>std</a>::<wbr><a href='index.html'>cell</a></p><script>window.sidebarCurrent = {name: 'Ref', ty: 'struct', 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"> </div> </form> </nav> <section id='main' class="content"> <h1 class='fqn'><span class='in-band'>Struct <a href='../index.html'>std</a>::<wbr><a href='index.html'>cell</a>::<wbr><a class="struct" href=''>Ref</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/cell.rs.html#983-986' title='goto source code'>[src]</a></span></h1> <pre class='rust struct'>pub struct Ref<'b, T> <span class="where fmt-newline">where<br> T: 'b + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span> { /* fields omitted */ }</pre><div class='docblock'><p>Wraps a borrowed reference to a value in a <code>RefCell</code> box. A wrapper type for an immutably borrowed value from a <code>RefCell<T></code>.</p> <p>See the <a href="index.html">module-level documentation</a> for more.</p> </div> <h2 id='methods' class='small-section-header'> Methods<a href='#methods' class='anchor'></a> </h2> <h3 id='impl' class='impl'><span class='in-band'><code>impl<'b, T> <a class="struct" href="../../std/cell/struct.Ref.html" title="struct std::cell::Ref">Ref</a><'b, T> <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code><a href='#impl' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/cell.rs.html#998-1044' 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>pub fn <a href='#method.clone' class='fnname'>clone</a>(orig: &<a class="struct" href="../../std/cell/struct.Ref.html" title="struct std::cell::Ref">Ref</a><'b, T>) -> <a class="struct" href="../../std/cell/struct.Ref.html" title="struct std::cell::Ref">Ref</a><'b, T></code></span><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.15.0'>1.15.0</div><a class='srclink' href='../../src/core/cell.rs.html#1009-1014' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Copies a <code>Ref</code>.</p> <p>The <code>RefCell</code> is already immutably borrowed, so this cannot fail.</p> <p>This is an associated function that needs to be used as <code>Ref::clone(...)</code>. A <code>Clone</code> implementation or a method would interfere with the widespread use of <code>r.borrow().clone()</code> to clone the contents of a <code>RefCell</code>.</p> </div><h4 id='method.map' class="method"><span id='map.v' class='invisible'><code>pub fn <a href='#method.map' class='fnname'>map</a><U, F>(orig: <a class="struct" href="../../std/cell/struct.Ref.html" title="struct std::cell::Ref">Ref</a><'b, T>, f: F) -> <a class="struct" href="../../std/cell/struct.Ref.html" title="struct std::cell::Ref">Ref</a><'b, U> <span class="where fmt-newline">where<br> F: <a class="trait" href="../../std/ops/trait.FnOnce.html" title="trait std::ops::FnOnce">FnOnce</a>(<a class="primitive" href="../primitive.reference.html">&</a>T) -> <a class="primitive" href="../primitive.reference.html">&</a>U,<br> U: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.8.0'>1.8.0</div><a class='srclink' href='../../src/core/cell.rs.html#1036-1043' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Make a new <code>Ref</code> for a component of the borrowed data.</p> <p>The <code>RefCell</code> is already immutably borrowed, so this cannot fail.</p> <p>This is an associated function that needs to be used as <code>Ref::map(...)</code>. A method would interfere with methods of the same name on the contents of a <code>RefCell</code> used through <code>Deref</code>.</p> <h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">cell</span>::{<span class="ident">RefCell</span>, <span class="ident">Ref</span>}; <span class="kw">let</span> <span class="ident">c</span> <span class="op">=</span> <span class="ident">RefCell</span>::<span class="ident">new</span>((<span class="number">5</span>, <span class="string">'b'</span>)); <span class="kw">let</span> <span class="ident">b1</span>: <span class="ident">Ref</span><span class="op"><</span>(<span class="ident">u32</span>, <span class="ident">char</span>)<span class="op">></span> <span class="op">=</span> <span class="ident">c</span>.<span class="ident">borrow</span>(); <span class="kw">let</span> <span class="ident">b2</span>: <span class="ident">Ref</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="ident">Ref</span>::<span class="ident">map</span>(<span class="ident">b1</span>, <span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="kw-2">&</span><span class="ident">t</span>.<span class="number">0</span>); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">b2</span>, <span class="number">5</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%3Acell%3A%3A%7BRefCell%2C%20Ref%7D%3B%0A%0Alet%20c%20%3D%20RefCell%3A%3Anew((5%2C%20'b'))%3B%0Alet%20b1%3A%20Ref%3C(u32%2C%20char)%3E%20%3D%20c.borrow()%3B%0Alet%20b2%3A%20Ref%3Cu32%3E%20%3D%20Ref%3A%3Amap(b1%2C%20%7Ct%7C%20%26t.0)%3B%0Aassert_eq!(*b2%2C%205)%0A%7D">Run</a></pre> </div></div> <h2 id='implementations' class='small-section-header'> Trait Implementations<a href='#implementations' class='anchor'></a> </h2> <h3 id='impl-Debug' class='impl'><span class='in-band'><code>impl<'b, T> <a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a> for <a class="struct" href="../../std/cell/struct.Ref.html" title="struct std::cell::Ref">Ref</a><'b, T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code><a href='#impl-Debug' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1807-1811' 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='../../std/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class="struct" href="../../std/fmt/struct.Formatter.html" title="struct std::fmt::Formatter">Formatter</a>) -> <a class="enum" href="../../std/result/enum.Result.html" title="enum std::result::Result">Result</a><<a class="primitive" href="../primitive.unit.html">()</a>, <a class="struct" href="../../std/fmt/struct.Error.html" title="struct std::fmt::Error">Error</a>></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1808-1810' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Formats the value using the given formatter. <a href="../../std/fmt/trait.Debug.html#tymethod.fmt">Read more</a></p> </div></div><h3 id='impl-CoerceUnsized%3CRef%3C%27b%2C%20U%3E%3E' class='impl'><span class='in-band'><code>impl<'b, T, U> <a class="trait" href="../../std/ops/trait.CoerceUnsized.html" title="trait std::ops::CoerceUnsized">CoerceUnsized</a><<a class="struct" href="../../std/cell/struct.Ref.html" title="struct std::cell::Ref">Ref</a><'b, U>> for <a class="struct" href="../../std/cell/struct.Ref.html" title="struct std::cell::Ref">Ref</a><'b, T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/marker/trait.Unsize.html" title="trait std::marker::Unsize">Unsize</a><U> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>,<br> U: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code><a href='#impl-CoerceUnsized%3CRef%3C%27b%2C%20U%3E%3E' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/cell.rs.html#1047' title='goto source code'>[src]</a></span></h3> <div class='impl-items'></div><h3 id='impl-Deref' class='impl'><span class='in-band'><code>impl<'b, T> <a class="trait" href="../../std/ops/trait.Deref.html" title="trait std::ops::Deref">Deref</a> for <a class="struct" href="../../std/cell/struct.Ref.html" title="struct std::cell::Ref">Ref</a><'b, T> <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code><a href='#impl-Deref' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/cell.rs.html#989-996' title='goto source code'>[src]</a></span></h3> <div class='impl-items'><h4 id='associatedtype.Target' class="type"><span id='Target.t' class='invisible'><code>type <a href='../../std/ops/trait.Deref.html#associatedtype.Target' class="type">Target</a> = T</code></span></h4> <div class='docblock'><p>The resulting type after dereferencing.</p> </div><h4 id='method.deref' class="method"><div class="important-traits"><div class='tooltip'>ⓘ<span class='tooltiptext'>Important traits for <a class="primitive" href="../primitive.reference.html">&'a mut </a>I</span></div><div class="content hidden"><h3 class="important">Important traits for <a class="primitive" href="../primitive.reference.html">&'a mut </a>I</h3><code class="content"><span class="where fmt-newline">impl<'a, I> <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> for <a class="primitive" href="../primitive.reference.html">&'a mut </a>I <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></span><span class="where fmt-newline"> type <a href='../../std/iter/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = <I as <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a>>::<a class="type" href="../../std/iter/trait.Iterator.html#associatedtype.Item" title="type std::iter::Iterator::Item">Item</a>;</span><span class="where fmt-newline">impl<'a, R: <a class="trait" href="../../std/io/trait.Read.html" title="trait std::io::Read">Read</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>> <a class="trait" href="../../std/io/trait.Read.html" title="trait std::io::Read">Read</a> for <a class="primitive" href="../primitive.reference.html">&'a mut </a>R</span><span class="where fmt-newline">impl<'a, W: <a class="trait" href="../../std/io/trait.Write.html" title="trait std::io::Write">Write</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>> <a class="trait" href="../../std/io/trait.Write.html" title="trait std::io::Write">Write</a> for <a class="primitive" href="../primitive.reference.html">&'a mut </a>W</span></code></div></div><span id='deref.v' class='invisible'><code>fn <a href='../../std/ops/trait.Deref.html#tymethod.deref' class='fnname'>deref</a>(&self) -> <a class="primitive" href="../primitive.reference.html">&</a>T</code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/cell.rs.html#993-995' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Dereferences the value.</p> </div></div><h3 id='impl-Display' class='impl'><span class='in-band'><code>impl<'a, T> <a class="trait" href="../../std/fmt/trait.Display.html" title="trait std::fmt::Display">Display</a> for <a class="struct" href="../../std/cell/struct.Ref.html" title="struct std::cell::Ref">Ref</a><'a, T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/fmt/trait.Display.html" title="trait std::fmt::Display">Display</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code><a href='#impl-Display' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.20.0'>1.20.0</div><a class='srclink' href='../../src/core/cell.rs.html#1050-1054' title='goto source code'>[src]</a></span></h3> <div class='impl-items'><h4 id='method.fmt-1' class="method"><span id='fmt.v-1' class='invisible'><code>fn <a href='../../std/fmt/trait.Display.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class="struct" href="../../std/fmt/struct.Formatter.html" title="struct std::fmt::Formatter">Formatter</a>) -> <a class="enum" href="../../std/result/enum.Result.html" title="enum std::result::Result">Result</a><<a class="primitive" href="../primitive.unit.html">()</a>, <a class="struct" href="../../std/fmt/struct.Error.html" title="struct std::fmt::Error">Error</a>></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/cell.rs.html#1051-1053' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Formats the value using the given formatter. <a href="../../std/fmt/trait.Display.html#tymethod.fmt">Read more</a></p> </div></div></section> <section id='search' class="content hidden"></section> <section class="footer"></section> <aside id="help" class="hidden"> <div> <h1 class="hidden">Help</h1> <div class="shortcuts"> <h2>Keyboard Shortcuts</h2> <dl> <dt><kbd>?</kbd></dt> <dd>Show this help dialog</dd> <dt><kbd>S</kbd></dt> <dd>Focus the search field</dd> <dt><kbd>↑</kbd></dt> <dd>Move up in search results</dd> <dt><kbd>↓</kbd></dt> <dd>Move down in search results</dd> <dt><kbd>↹</kbd></dt> <dd>Switch tab</dd> <dt><kbd>⏎</kbd></dt> <dd>Go to active search result</dd> <dt><kbd>+</kbd></dt> <dd>Expand all sections</dd> <dt><kbd>-</kbd></dt> <dd>Collapse all sections</dd> </dl> </div> <div class="infos"> <h2>Search Tricks</h2> <p> Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type. </p> <p> Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>. </p> <p> Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>) </p> </div> </div> </aside> <script> window.rootPath = "../../"; window.currentCrate = "std"; </script> <script src="../../main.js"></script> <script defer src="../../search-index.js"></script> </body> </html>