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<!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="A trait for types that can be used to replace matches in a haystack."><title>Replacer in regex::bytes - Rust</title><script> if (window.location.protocol !== "file:") document.write(`<link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2">`)</script><link rel="stylesheet" href="../../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../../static.files/rustdoc-e935ef01ae1c1829.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="regex" data-themes="" data-resource-suffix="" data-rustdoc-version="1.78.0 (9b00956e5 2024-04-29)" data-channel="1.78.0" data-search-js="search-42d8da7a6b9792c2.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../../static.files/storage-4c98445ec4002617.js"></script><script defer src="sidebar-items.js"></script><script defer src="../../static.files/main-12cf3b4f4f9dc36d.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-04d5337699b92874.css"></noscript><link rel="alternate icon" type="image/png" href="../../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc trait"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle" title="show sidebar"></button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../../regex/index.html">regex</a><span class="version">1.10.4</span></h2></div><h2 class="location"><a href="#">Replacer</a></h2><div class="sidebar-elems"><section><h3><a href="#required-methods">Required Methods</a></h3><ul class="block"><li><a href="#tymethod.replace_append">replace_append</a></li></ul><h3><a href="#provided-methods">Provided Methods</a></h3><ul class="block"><li><a href="#method.by_ref">by_ref</a></li><li><a href="#method.no_expansion">no_expansion</a></li></ul><h3><a href="#foreign-impls">Implementations on Foreign Types</a></h3><ul class="block"><li><a href="#impl-Replacer-for-%26Cow%3C'a,+%5Bu8%5D%3E">&amp;&#x27;a Cow&lt;&#x27;a, [u8]&gt;</a></li><li><a href="#impl-Replacer-for-%26Vec%3Cu8%3E">&amp;&#x27;a Vec&lt;u8&gt;</a></li><li><a href="#impl-Replacer-for-%26%5Bu8;+N%5D">&amp;&#x27;a [u8; N]</a></li><li><a href="#impl-Replacer-for-%26%5Bu8%5D">&amp;&#x27;a [u8]</a></li><li><a href="#impl-Replacer-for-Cow%3C'a,+%5Bu8%5D%3E">Cow&lt;&#x27;a, [u8]&gt;</a></li><li><a href="#impl-Replacer-for-Vec%3Cu8%3E">Vec&lt;u8&gt;</a></li><li><a href="#impl-Replacer-for-%5Bu8;+N%5D">[u8; N]</a></li></ul><h3><a href="#object-safety">Object Safety</a></h3><h3><a href="#implementors">Implementors</a></h3></section><h2><a href="index.html">In regex::bytes</a></h2></div></nav><div class="sidebar-resizer"></div>
<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../../regex/all.html" title="show sidebar"></a></div><input class="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"><div id="help-button" tabindex="-1"><a href="../../help.html" title="help">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Trait <a href="../index.html">regex</a>::<wbr><a href="index.html">bytes</a>::<wbr><a class="trait" href="#">Replacer</a><button id="copy-path" title="Copy item path to clipboard"><img src="../../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="src" href="../../src/regex/regex/bytes.rs.html#2428-2475">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>&#x2212;</span>]</button></span></div><pre class="rust item-decl"><code>pub trait Replacer {
// Required method
fn <a href="#tymethod.replace_append" class="fn">replace_append</a>(&amp;mut self, caps: &amp;<a class="struct" href="struct.Captures.html" title="struct regex::bytes::Captures">Captures</a>&lt;'_&gt;, dst: &amp;mut <a class="struct" href="https://doc.rust-lang.org/1.78.0/alloc/vec/struct.Vec.html" title="struct alloc::vec::Vec">Vec</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.u8.html">u8</a>&gt;);
// Provided methods
fn <a href="#method.no_expansion" class="fn">no_expansion</a>&lt;'r&gt;(&amp;'r mut self) -&gt; <a class="enum" href="https://doc.rust-lang.org/1.78.0/core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;<a class="enum" href="https://doc.rust-lang.org/1.78.0/alloc/borrow/enum.Cow.html" title="enum alloc::borrow::Cow">Cow</a>&lt;'r, [<a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.u8.html">u8</a>]&gt;&gt; { ... }
<span class="item-spacer"></span> fn <a href="#method.by_ref" class="fn">by_ref</a>&lt;'r&gt;(&amp;'r mut self) -&gt; <a class="struct" href="struct.ReplacerRef.html" title="struct regex::bytes::ReplacerRef">ReplacerRef</a>&lt;'r, Self&gt; { ... }
}</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>A trait for types that can be used to replace matches in a haystack.</p>
<p>In general, users of this crate shouldnt need to implement this trait,
since implementations are already provided for <code>&amp;[u8]</code> along with other
variants of byte string types, as well as <code>FnMut(&amp;Captures) -&gt; Vec&lt;u8&gt;</code> (or
any <code>FnMut(&amp;Captures) -&gt; T</code> where <code>T: AsRef&lt;[u8]&gt;</code>). Those cover most use
cases, but callers can implement this trait directly if necessary.</p>
<h2 id="example"><a class="doc-anchor" href="#example">§</a>Example</h2>
<p>This example shows a basic implementation of the <code>Replacer</code> trait. This can
be done much more simply using the replacement byte string interpolation
support (e.g., <code>$first $last</code>), but this approach avoids needing to parse
the replacement byte string at all.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>regex::bytes::{Captures, Regex, Replacer};
<span class="kw">struct </span>NameSwapper;
<span class="kw">impl </span>Replacer <span class="kw">for </span>NameSwapper {
<span class="kw">fn </span>replace_append(<span class="kw-2">&amp;mut </span><span class="self">self</span>, caps: <span class="kw-2">&amp;</span>Captures&lt;<span class="lifetime">'_</span>&gt;, dst: <span class="kw-2">&amp;mut </span>Vec&lt;u8&gt;) {
dst.extend_from_slice(<span class="kw-2">&amp;</span>caps[<span class="string">"first"</span>]);
dst.extend_from_slice(<span class="string">b" "</span>);
dst.extend_from_slice(<span class="kw-2">&amp;</span>caps[<span class="string">"last"</span>]);
}
}
<span class="kw">let </span>re = Regex::new(<span class="string">r"(?&lt;last&gt;[^,\s]+),\s+(?&lt;first&gt;\S+)"</span>).unwrap();
<span class="kw">let </span>result = re.replace(<span class="string">b"Springsteen, Bruce"</span>, NameSwapper);
<span class="macro">assert_eq!</span>(result, <span class="kw-2">&amp;</span><span class="string">b"Bruce Springsteen"</span>[..]);</code></pre></div>
</div></details><h2 id="required-methods" class="section-header">Required Methods<a href="#required-methods" class="anchor">§</a></h2><div class="methods"><details class="toggle method-toggle" open><summary><section id="tymethod.replace_append" class="method"><a class="src rightside" href="../../src/regex/regex/bytes.rs.html#2436">source</a><h4 class="code-header">fn <a href="#tymethod.replace_append" class="fn">replace_append</a>(&amp;mut self, caps: &amp;<a class="struct" href="struct.Captures.html" title="struct regex::bytes::Captures">Captures</a>&lt;'_&gt;, dst: &amp;mut <a class="struct" href="https://doc.rust-lang.org/1.78.0/alloc/vec/struct.Vec.html" title="struct alloc::vec::Vec">Vec</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.u8.html">u8</a>&gt;)</h4></section></summary><div class="docblock"><p>Appends possibly empty data to <code>dst</code> to replace the current match.</p>
<p>The current match is represented by <code>caps</code>, which is guaranteed to have
a match at capture group <code>0</code>.</p>
<p>For example, a no-op replacement would be
<code>dst.extend_from_slice(&amp;caps[0])</code>.</p>
</div></details></div><h2 id="provided-methods" class="section-header">Provided Methods<a href="#provided-methods" class="anchor">§</a></h2><div class="methods"><details class="toggle method-toggle" open><summary><section id="method.no_expansion" class="method"><a class="src rightside" href="../../src/regex/regex/bytes.rs.html#2446-2448">source</a><h4 class="code-header">fn <a href="#method.no_expansion" class="fn">no_expansion</a>&lt;'r&gt;(&amp;'r mut self) -&gt; <a class="enum" href="https://doc.rust-lang.org/1.78.0/core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;<a class="enum" href="https://doc.rust-lang.org/1.78.0/alloc/borrow/enum.Cow.html" title="enum alloc::borrow::Cow">Cow</a>&lt;'r, [<a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.u8.html">u8</a>]&gt;&gt;</h4></section></summary><div class="docblock"><p>Return a fixed unchanging replacement byte string.</p>
<p>When doing replacements, if access to <a href="struct.Captures.html" title="struct regex::bytes::Captures"><code>Captures</code></a> is not needed (e.g.,
the replacement byte 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 <a href="struct.Regex.html#method.replace_all" title="method regex::bytes::Regex::replace_all"><code>Regex::replace_all</code></a>.</p>
</div></details><details class="toggle method-toggle" open><summary><section id="method.by_ref" class="method"><a class="src rightside" href="../../src/regex/regex/bytes.rs.html#2472-2474">source</a><h4 class="code-header">fn <a href="#method.by_ref" class="fn">by_ref</a>&lt;'r&gt;(&amp;'r mut self) -&gt; <a class="struct" href="struct.ReplacerRef.html" title="struct regex::bytes::ReplacerRef">ReplacerRef</a>&lt;'r, Self&gt;</h4></section></summary><div class="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
more than once.</p>
<h5 id="example-1"><a class="doc-anchor" href="#example-1">§</a>Example</h5>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>regex::bytes::{Regex, Replacer};
<span class="kw">fn </span>replace_all_twice&lt;R: Replacer&gt;(
re: Regex,
src: <span class="kw-2">&amp;</span>[u8],
<span class="kw-2">mut </span>rep: R,
) -&gt; Vec&lt;u8&gt; {
<span class="kw">let </span>dst = re.replace_all(src, rep.by_ref());
<span class="kw">let </span>dst = re.replace_all(<span class="kw-2">&amp;</span>dst, rep.by_ref());
dst.into_owned()
}</code></pre></div>
</div></details></div><h2 id="object-safety" class="section-header">Object Safety<a href="#object-safety" class="anchor">§</a></h2><div class="object-safety-info">This trait is <b>not</b> <a href="https://doc.rust-lang.org/1.78.0/reference/items/traits.html#object-safety">object safe</a>.</div><h2 id="foreign-impls" class="section-header">Implementations on Foreign Types<a href="#foreign-impls" class="anchor">§</a></h2><details class="toggle implementors-toggle"><summary><section id="impl-Replacer-for-Vec%3Cu8%3E" class="impl"><a class="src rightside" href="../../src/regex/regex/bytes.rs.html#2517-2525">source</a><a href="#impl-Replacer-for-Vec%3Cu8%3E" class="anchor">§</a><h3 class="code-header">impl <a class="trait" href="trait.Replacer.html" title="trait regex::bytes::Replacer">Replacer</a> for <a class="struct" href="https://doc.rust-lang.org/1.78.0/alloc/vec/struct.Vec.html" title="struct alloc::vec::Vec">Vec</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.u8.html">u8</a>&gt;</h3></section></summary><div class="impl-items"><section id="method.replace_append" class="method trait-impl"><a class="src rightside" href="../../src/regex/regex/bytes.rs.html#2518-2520">source</a><a href="#method.replace_append" class="anchor">§</a><h4 class="code-header">fn <a href="#tymethod.replace_append" class="fn">replace_append</a>(&amp;mut self, caps: &amp;<a class="struct" href="struct.Captures.html" title="struct regex::bytes::Captures">Captures</a>&lt;'_&gt;, dst: &amp;mut <a class="struct" href="https://doc.rust-lang.org/1.78.0/alloc/vec/struct.Vec.html" title="struct alloc::vec::Vec">Vec</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.u8.html">u8</a>&gt;)</h4></section><section id="method.no_expansion-1" class="method trait-impl"><a class="src rightside" href="../../src/regex/regex/bytes.rs.html#2522-2524">source</a><a href="#method.no_expansion-1" class="anchor">§</a><h4 class="code-header">fn <a href="#method.no_expansion" class="fn">no_expansion</a>(&amp;mut self) -&gt; <a class="enum" href="https://doc.rust-lang.org/1.78.0/core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;<a class="enum" href="https://doc.rust-lang.org/1.78.0/alloc/borrow/enum.Cow.html" title="enum alloc::borrow::Cow">Cow</a>&lt;'_, [<a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.u8.html">u8</a>]&gt;&gt;</h4></section></div></details><details class="toggle implementors-toggle"><summary><section id="impl-Replacer-for-%26Cow%3C'a,+%5Bu8%5D%3E" class="impl"><a class="src rightside" href="../../src/regex/regex/bytes.rs.html#2537-2545">source</a><a href="#impl-Replacer-for-%26Cow%3C'a,+%5Bu8%5D%3E" class="anchor">§</a><h3 class="code-header">impl&lt;'a&gt; <a class="trait" href="trait.Replacer.html" title="trait regex::bytes::Replacer">Replacer</a> for &amp;'a <a class="enum" href="https://doc.rust-lang.org/1.78.0/alloc/borrow/enum.Cow.html" title="enum alloc::borrow::Cow">Cow</a>&lt;'a, [<a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.u8.html">u8</a>]&gt;</h3></section></summary><div class="impl-items"><section id="method.replace_append-1" class="method trait-impl"><a class="src rightside" href="../../src/regex/regex/bytes.rs.html#2538-2540">source</a><a href="#method.replace_append-1" class="anchor">§</a><h4 class="code-header">fn <a href="#tymethod.replace_append" class="fn">replace_append</a>(&amp;mut self, caps: &amp;<a class="struct" href="struct.Captures.html" title="struct regex::bytes::Captures">Captures</a>&lt;'_&gt;, dst: &amp;mut <a class="struct" href="https://doc.rust-lang.org/1.78.0/alloc/vec/struct.Vec.html" title="struct alloc::vec::Vec">Vec</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.u8.html">u8</a>&gt;)</h4></section><section id="method.no_expansion-2" class="method trait-impl"><a class="src rightside" href="../../src/regex/regex/bytes.rs.html#2542-2544">source</a><a href="#method.no_expansion-2" class="anchor">§</a><h4 class="code-header">fn <a href="#met
F: <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/ops/function/trait.FnMut.html" title="trait core::ops::function::FnMut">FnMut</a>(&amp;<a class="struct" href="struct.Captures.html" title="struct regex::bytes::Captures">Captures</a>&lt;'_&gt;) -&gt; T,
T: <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.AsRef.html" title="trait core::convert::AsRef">AsRef</a>&lt;[<a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.u8.html">u8</a>]&gt;,</div></h3></section></div><script src="../../trait.impl/regex/regex/bytes/trait.Replacer.js" data-ignore-extern-crates="alloc,std" async></script></section></div></main></body></html>