<!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 `DebugMap` struct in crate `std`."> <meta name="keywords" content="rust, rustlang, rust-lang, DebugMap"> <title>std::fmt::DebugMap - 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 DebugMap</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#methods">Methods</a><div class="sidebar-links"><a href="#method.entry">entry</a><a href="#method.entries">entries</a><a href="#method.finish">finish</a></div></div><p class='location'><a href='../index.html'>std</a>::<wbr><a href='index.html'>fmt</a></p><script>window.sidebarCurrent = {name: 'DebugMap', 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'>fmt</a>::<wbr><a class="struct" href=''>DebugMap</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.2.0'>1.2.0</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/fmt/builders.rs.html#467-471' title='goto source code'>[src]</a></span></h1> <pre class='rust struct'><div class="docblock attributes">#[must_use] </div>pub struct DebugMap<'a, 'b> <span class="where fmt-newline">where<br> 'b: 'a, </span> { /* fields omitted */ }</pre><div class='docblock'><p>A struct to help with <a href="trait.Debug.html"><code>fmt::Debug</code></a> implementations.</p> <p>This is useful when you wish to output a formatted map as a part of your <a href="trait.Debug.html#tymethod.fmt"><code>Debug::fmt</code></a> implementation.</p> <p>This can be constructed by the <a href="struct.Formatter.html#method.debug_map"><code>Formatter::debug_map</code></a> method.</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">fmt</span>; <span class="kw">struct</span> <span class="ident">Foo</span>(<span class="ident">Vec</span><span class="op"><</span>(<span class="ident">String</span>, <span class="ident">i32</span>)<span class="op">></span>); <span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Foo</span> { <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">fmt</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> { <span class="ident">fmt</span>.<span class="ident">debug_map</span>().<span class="ident">entries</span>(<span class="self">self</span>.<span class="number">0</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="op">|</span><span class="kw-2">&</span>(<span class="kw-2">ref</span> <span class="ident">k</span>, <span class="kw-2">ref</span> <span class="ident">v</span>)<span class="op">|</span> (<span class="ident">k</span>, <span class="ident">v</span>))).<span class="ident">finish</span>() } } <span class="comment">// prints "{"A": 10, "B": 11}"</span> <span class="macro">println</span><span class="macro">!</span>(<span class="string">"{:?}"</span>, <span class="ident">Foo</span>(<span class="macro">vec</span><span class="macro">!</span>[(<span class="string">"A"</span>.<span class="ident">to_string</span>(), <span class="number">10</span>), (<span class="string">"B"</span>.<span class="ident">to_string</span>(), <span class="number">11</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%3Afmt%3B%0A%0Astruct%20Foo(Vec%3C(String%2C%20i32)%3E)%3B%0A%0Aimpl%20fmt%3A%3ADebug%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20fmt%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20fmt.debug_map().entries(self.0.iter().map(%7C%26(ref%20k%2C%20ref%20v)%7C%20(k%2C%20v))).finish()%0A%20%20%20%20%7D%0A%7D%0A%0A%2F%2F%20prints%20%22%7B%22A%22%3A%2010%2C%20%22B%22%3A%2011%7D%22%0Aprintln!(%22%7B%3A%3F%7D%22%2C%20Foo(vec!%5B(%22A%22.to_string()%2C%2010)%2C%20(%22B%22.to_string()%2C%2011)%5D))%3B%0A%7D">Run</a></pre> </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<'a, 'b> <a class="struct" href="../../std/fmt/struct.DebugMap.html" title="struct std::fmt::DebugMap">DebugMap</a><'a, 'b> <span class="where fmt-newline">where<br> 'b: '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/fmt/builders.rs.html#482-539' title='goto source code'>[src]</a></span></h3> <div class='impl-items'><h4 id='method.entry' class="method"><span id='entry.v' class='invisible'><code>pub fn <a href='#method.entry' class='fnname'>entry</a>(&mut self, key: &<a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a>, value: &<a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a>) -> &mut <a class="struct" href="../../std/fmt/struct.DebugMap.html" title="struct std::fmt::DebugMap">DebugMap</a><'a, 'b></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/builders.rs.html#485-510' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Adds a new entry to the map output.</p> </div><h4 id='method.entries' class="method"><span id='entries.v' class='invisible'><code>pub fn <a href='#method.entries' class='fnname'>entries</a><K, V, I>(&mut self, entries: I) -> &mut <a class="struct" href="../../std/fmt/struct.DebugMap.html" title="struct std::fmt::DebugMap">DebugMap</a><'a, 'b> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.IntoIterator.html" title="trait std::iter::IntoIterator">IntoIterator</a><Item = <a class="primitive" href="../primitive.tuple.html">(</a>K, V<a class="primitive" href="../primitive.tuple.html">)</a>>,<br> K: <a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a>,<br> V: <a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/builders.rs.html#514-523' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Adds the contents of an iterator of entries to the map output.</p> </div><h4 id='method.finish' class="method"><span id='finish.v' class='invisible'><code>pub fn <a href='#method.finish' class='fnname'>finish</a>(&mut self) -> <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/builders.rs.html#527-534' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Finishes output and returns any error encountered.</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> 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