<!DOCTYPE html><htmllang="en"><head><metacharset="utf-8"><metaname="viewport"content="width=device-width, initial-scale=1.0"><metaname="generator"content="rustdoc"><metaname="description"content="A trait for types that can be used to replace matches in a haystack."><title>Replacer in regex - Rust</title><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><linkrel="stylesheet"href="../static.files/normalize-76eba96aa4d2e634.css"><linkrel="stylesheet"href="../static.files/rustdoc-5bc39a1768837dd0.css"><metaname="rustdoc-vars"data-root-path="../"data-static-root-path="../static.files/"data-current-crate="regex"data-themes=""data-resource-suffix=""data-rustdoc-version="1.77.0 (aedd173a2 2024-03-17)"data-channel="1.77.0"data-search-js="search-dd67cee4cfa65049.js"data-settings-js="settings-4313503d2e1961c2.js"><scriptsrc="../static.files/storage-4c98445ec4002617.js"></script><scriptdefersrc="sidebar-items.js"></script><scriptdefersrc="../static.files/main-48f368f3872407c8.js"></script><noscript><linkrel="stylesheet"href="../static.files/noscript-04d5337699b92874.css"></noscript><linkrel="alternate icon"type="image/png"href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><linkrel="alternate icon"type="image/png"href="../static.files/favicon-32x32-422f7d1d52889060.png"><linkrel="icon"type="image/svg+xml"href="../static.files/favicon-2c020d218678b618.svg"></head><bodyclass="rustdoc trait"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><navclass="mobile-topbar"><buttonclass="sidebar-menu-toggle"title="show sidebar"></button></nav><navclass="sidebar"><divclass="sidebar-crate"><h2><ahref="../regex/index.html">regex</a><spanclass="version">1.10.3</span></h2></div><h2class="location"><ahref="#">Replacer</a></h2><divclass="sidebar-elems"><section><h3><ahref="#required-methods">Required Methods</a></h3><ulclass="block"><li><ahref="#tymethod.replace_append">replace_append</a></li></ul><h3><ahref="#provided-methods">Provided Methods</a></h3><ulclass="block"><li><ahref="#method.by_ref">by_ref</a></li><li><ahref="#method.no_expansion">no_expansion</a></li></ul><h3><ahref="#foreign-impls">Implementations on Foreign Types</a></h3><ulclass="block"><li><ahref="#impl-Replacer-for-%26Cow%3C'a,+str%3E">&'a Cow<'a, str></a></li><li><ahref="#impl-Replacer-for-%26String">&'a String</a></li><li><ahref="#impl-Replacer-for-%26str">&'a str</a></li><li><ahref="#impl-Replacer-for-Cow%3C'a,+str%3E">Cow<'a, str></a></li><li><ahref="#impl-Replacer-for-String">String</a></li></ul><h3><ahref="#object-safety">Object Safety</a></h3><h3><ahref="#implementors">Implementors</a></h3></section><h2><ahref="index.html">In crate regex</a></h2></div></nav><divclass="sidebar-resizer"></div>
<main><divclass="width-limiter"><navclass="sub"><formclass="search-form"><span></span><divid="sidebar-button"tabindex="-1"><ahref="../regex/all.html"title="show sidebar"></a></div><inputclass="search-input"name="search"aria-label="Run search in the documentation"autocomplete="off"spellcheck="false"placeholder="Click or press ‘S’ to search, ‘?’ for more options…"type="search"><divid="help-button"tabindex="-1"><ahref="../help.html"title="help">?</a></div><divid="settings-menu"tabindex="-1"><ahref="../settings.html"title="settings"><imgwidth="22"height="22"alt="Change settings"src="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><sectionid="main-content"class="content"><divclass="main-heading"><h1>Trait <ahref="index.html">regex</a>::<wbr><aclass="trait"href="#">Replacer</a><buttonid="copy-path"title="Copy item path to clipboard"><imgsrc="../static.files/clipboard-7571035ce49a181d.svg"width="19"height="18"alt="Copy item path"></button></h1><spanclass="out-of-band"><aclass="src"href="../src/regex/regex/string.rs.html#2414-2460">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><preclass="rust item-decl"><code>pub trait Replacer {
}</code></pre><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>A trait for types that can be used to replace matches in a haystack.</p>
<p>In general, users of this crate shouldn’t need to implement this trait,
since implementations are already provided for <code>&str</code> along with other
variants of string types, as well as <code>FnMut(&Captures) -> String</code> (or any
<code>FnMut(&Captures) -> T</code> where <code>T: AsRef<str></code>). Those cover most use cases,
but callers can implement this trait directly if necessary.</p>
</div></details><h2id="required-methods"class="section-header">Required Methods<ahref="#required-methods"class="anchor">§</a></h2><divclass="methods"><detailsclass="toggle method-toggle"open><summary><sectionid="tymethod.replace_append"class="method"><aclass="src rightside"href="../src/regex/regex/string.rs.html#2421">source</a><h4class="code-header">fn <ahref="#tymethod.replace_append"class="fn">replace_append</a>(&mut self, caps: &<aclass="struct"href="struct.Captures.html"title="struct regex::Captures">Captures</a><'_>, dst: &mut <aclass="struct"href="https://doc.rust-lang.org/1.77.0/alloc/string/struct.String.html"title="struct alloc::string::String">String</a>)</h4></section></summary><divclass="docblock"><p>Appends possibly empty data to <code>dst</code> to replace the current match.</p>
<p>When doing replacements, if access to <ahref="struct.Captures.html"title="struct regex::Captures"><code>Captures</code></a> is not needed (e.g.,
the replacement string does not need <code>$</code> expansion), then it can be
beneficial to avoid finding sub-captures.</p>
<p>In general, this is called once for every call to a replacement routine
such as <ahref="struct.Regex.html#method.replace_all"title="method regex::Regex::replace_all"><code>Regex::replace_all</code></a>.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.by_ref"class="method"><aclass="src rightside"href="../src/regex/regex/string.rs.html#2457-2459">source</a><h4class="code-header">fn <ahref="#method.by_ref"class="fn">by_ref</a><'r>(&'r mut self) -><aclass="struct"href="struct.ReplacerRef.html"title="struct regex::ReplacerRef">ReplacerRef</a><'r, Self></h4></section></summary><divclass="docblock"><p>Returns a type that implements <code>Replacer</code>, but that borrows and wraps
this <code>Replacer</code>.</p>
<p>This is useful when you want to take a generic <code>Replacer</code> (which might
not be cloneable) and use it without consuming it, so it can be used
