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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="What `#[derive(Into)]` generates"><title>Into in derive_more_impl - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../static.files/rustdoc-42caa33d.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="derive_more_impl" data-themes="" data-resource-suffix="" data-rustdoc-version="1.84.0 (9fc6b4312 2025-01-07)" data-channel="1.84.0" data-search-js="search-92e6798f.js" data-settings-js="settings-0f613d39.js" ><script src="../static.files/storage-59e33391.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-5f194d8c.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-893ab5e7.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-6580c154.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-044be391.svg"></head><body class="rustdoc derive"><!--[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="../derive_more_impl/index.html">derive_<wbr>more_<wbr>impl</a><span class="version">1.0.0</span></h2></div><div class="sidebar-elems"><section id="rustdoc-toc"><h2 class="location"><a href="#">Into</a></h2><h3><a href="#">Sections</a></h3><ul class="block top-toc"><li><a href="#what-deriveinto-generates" title="What `#[derive(Into)]` generates">What <code>#[derive(Into)]</code> generates</a><ul><li><a href="#structs" title="Structs">Structs</a></li><li><a href="#enums" title="Enums">Enums</a></li></ul></li></ul></section><div id="rustdoc-modnav"><h2 class="in-crate"><a href="index.html">In crate derive_<wbr>more_<wbr>impl</a></h2></div></div></nav><div class="sidebar-resizer"></div><main><div class="width-limiter"><rustdoc-search></rustdoc-search><section id="main-content" class="content"><div class="main-heading"><span class="rustdoc-breadcrumbs"><a href="index.html">derive_more_impl</a></span><h1>Derive Macro <span class="derive">Into</span><button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../src/derive_more_impl/lib.rs.html#203">Source</a> </span></div><pre class="rust item-decl"><code>#[derive(Into)]
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{
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<span class="comment">// Attributes available to this derive:</span>
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#[into]
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}
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</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><h2 id="what-deriveinto-generates"><a class="doc-anchor" href="#what-deriveinto-generates">§</a>What <code>#[derive(Into)]</code> generates</h2>
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<p>This derive creates the exact opposite of <code>#[derive(From)]</code>.
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Instead of allowing you to create a new instance of the struct from the values
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it should contain, it allows you to extract the values from the struct. One
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thing to note is that this derive doesn’t actually generate an implementation
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for the <code>Into</code> trait. Instead, it derives <code>From</code> for the values contained in
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the struct and thus has an indirect implementation of <code>Into</code> as
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<a href="https://doc.rust-lang.org/core/convert/trait.Into.html">recommended by the docs</a>.</p>
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<h3 id="structs"><a class="doc-anchor" href="#structs">§</a>Structs</h3>
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<p>For structs with a single field you can call <code>.into()</code> to extract the inner type.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="attr">#[derive(Debug, Into, PartialEq)]
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</span><span class="kw">struct </span>Int(i32);
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<span class="macro">assert_eq!</span>(<span class="number">2</span>, Int(<span class="number">2</span>).into());</code></pre></div>
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<p>For structs having multiple fields, <code>.into()</code> extracts a tuple containing the
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desired content for each field.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="attr">#[derive(Debug, Into, PartialEq)]
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</span><span class="kw">struct </span>Point(i32, i32);
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<span class="macro">assert_eq!</span>((<span class="number">1</span>, <span class="number">2</span>), Point(<span class="number">1</span>, <span class="number">2</span>).into());</code></pre></div>
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<p>To specify concrete types for deriving conversions into, use <code>#[into(<types>)]</code>.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="attr">#[derive(Debug, Into, PartialEq)]
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#[into(Cow<<span class="lifetime">'static</span>, str>, String)]
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</span><span class="kw">struct </span>Str(Cow<<span class="lifetime">'static</span>, str>);
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<span class="macro">assert_eq!</span>(<span class="string">"String"</span>.to_owned(), String::from(Str(<span class="string">"String"</span>.into())));
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<span class="macro">assert_eq!</span>(Cow::Borrowed(<span class="string">"Cow"</span>), <Cow<<span class="kw">_</span>>>::from(Str(<span class="string">"Cow"</span>.into())));
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<span class="attr">#[derive(Debug, Into, PartialEq)]
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#[into((i64, i64), (i32, i32))]
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</span><span class="kw">struct </span>Point {
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x: i32,
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y: i32,
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}
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<span class="macro">assert_eq!</span>((<span class="number">1_i64</span>, <span class="number">2_i64</span>), Point { x: <span class="number">1_i32</span>, y: <span class="number">2_i32 </span>}.into());
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<span class="macro">assert_eq!</span>((<span class="number">3_i32</span>, <span class="number">4_i32</span>), Point { x: <span class="number">3_i32</span>, y: <span class="number">4_i32 </span>}.into());</code></pre></div>
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<p>In addition to converting to owned types, this macro supports deriving into
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reference (mutable or not) via <code>#[into(ref(...))]</code>/<code>#[into(ref_mut(...))]</code>.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="attr">#[derive(Debug, Into, PartialEq)]
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#[into(owned, <span class="kw-2">ref</span>(i32), ref_mut)]
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</span><span class="kw">struct </span>Int(i32);
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<span class="macro">assert_eq!</span>(<span class="number">2</span>, Int(<span class="number">2</span>).into());
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<span class="macro">assert_eq!</span>(<span class="kw-2">&</span><span class="number">2</span>, <<span class="kw-2">&</span>i32>::from(<span class="kw-2">&</span>Int(<span class="number">2</span>)));
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<span class="macro">assert_eq!</span>(<span class="kw-2">&mut </span><span class="number">2</span>, <<span class="kw-2">&mut </span>i32>::from(<span class="kw-2">&mut </span>Int(<span class="number">2</span>)));</code></pre></div>
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<p>In case there are fields, that shouldn’t be included in the conversion, use the
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<code>#[into(skip)]</code> (or <code>#[into(ignore)]</code>) attribute.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="attr">#[derive(Debug, Into, PartialEq)]
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#[into(i32, i64, i128)]
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</span><span class="kw">struct </span>Mass<Unit> {
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value: i32,
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<span class="attr">#[into(skip)] </span><span class="comment">// or #[into(ignore)]
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</span>_unit: PhantomData<Unit>,
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}
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<span class="macro">assert_eq!</span>(<span class="number">5</span>, Mass::<Gram>::new(<span class="number">5</span>).into());
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<span class="macro">assert_eq!</span>(<span class="number">5_i64</span>, Mass::<Gram>::new(<span class="number">5</span>).into());
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<span class="macro">assert_eq!</span>(<span class="number">5_i128</span>, Mass::<Gram>::new(<span class="number">5</span>).into());</code></pre></div>
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<h4 id="fields-1"><a class="doc-anchor" href="#fields-1">§</a>Fields</h4>
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<p>The <code>#[into]</code> attribute can also be applied to specific fields of a struct.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="attr">#[derive(Into)]
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</span><span class="kw">struct </span>Data {
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id: i32,
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<span class="attr">#[into]
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</span>raw: f64
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}
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<span class="macro">assert_eq!</span>(<span class="number">42.0</span>, Data { id: <span class="number">1</span>, raw: <span class="number">42.0 </span>}.into());</code></pre></div>
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<p>In such cases, no conversion into a tuple of all fields is generated, unless
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an explicit struct attribute is present.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="attr">#[derive(Into)]
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#[into]
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</span><span class="kw">struct </span>Data {
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id: i32,
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<span class="attr">#[into]
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</span>raw: f64
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}
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<span class="macro">assert_eq!</span>(<span class="number">42.0</span>, Data { id: <span class="number">1</span>, raw: <span class="number">42.0 </span>}.into());
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<span class="macro">assert_eq!</span>((<span class="number">1</span>, <span class="number">42.0</span>), Data { id: <span class="number">1</span>, raw: <span class="number">42.0 </span>}.into());</code></pre></div>
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<p>The <code>#[into(<types>)]</code> syntax can be used on fields as well.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="attr">#[derive(Into, Clone)]
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#[into(owned, <span class="kw-2">ref</span>((u8, str)), ref_mut)]
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</span><span class="kw">struct </span>Foo {
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<span class="attr">#[into(owned(u64), <span class="kw-2">ref</span>)]
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</span>a: u8,
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b: String,
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<span class="attr">#[into(skip)]
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</span>_c: PhantomData<Whatever>,
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}
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<span class="kw">let </span><span class="kw-2">mut </span>foo = Foo { a: <span class="number">1</span>, b: <span class="string">"string"</span>.to_owned(), _c: PhantomData };
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<span class="macro">assert_eq!</span>((<span class="number">1_u8</span>, <span class="string">"string"</span>.to_owned()), foo.clone().into());
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<span class="macro">assert_eq!</span>((<span class="kw-2">&</span><span class="number">1_u8</span>, <span class="string">"string"</span>), <(<span class="kw-2">&</span>u8, <span class="kw-2">&</span>str)>::from(<span class="kw-2">&</span>foo));
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<span class="macro">assert_eq!</span>((<span class="kw-2">&mut </span><span class="number">1_u8</span>, <span class="kw-2">&mut </span><span class="string">"string"</span>.to_owned()), <(<span class="kw-2">&mut </span>u8, <span class="kw-2">&mut </span>String)>::from(<span class="kw-2">&mut </span>foo));
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<span class="macro">assert_eq!</span>(<span class="number">1_u64</span>, foo.clone().into());
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<span class="macro">assert_eq!</span>(<span class="kw-2">&</span><span class="number">1_u8</span>, <<span class="kw-2">&</span>u8>::from(<span class="kw-2">&</span>foo));</code></pre></div>
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<p>Fields, having specific conversions into them, can also be skipped for top-level
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tuple conversions.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code>
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<span class="attr">#[derive(Into)]
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#[into(<span class="kw-2">ref</span>((str, f64)))]
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</span><span class="kw">struct </span>Foo {
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<span class="attr">#[into(<span class="kw-2">ref</span>)]
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#[into(skip)]
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</span>a: u8,
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b: String,
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c: f64,
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}
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<span class="kw">let </span>foo = Foo { a: <span class="number">1</span>, b: <span class="string">"string"</span>.to_owned(), c: <span class="number">3.0 </span>};
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<span class="macro">assert_eq!</span>((<span class="string">"string"</span>, <span class="kw-2">&</span><span class="number">3.0</span>), (<span class="kw-2">&</span>foo).into());
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<span class="macro">assert_eq!</span>(<span class="kw-2">&</span><span class="number">1_u8</span>, <<span class="kw-2">&</span>u8>::from(<span class="kw-2">&</span>foo));</code></pre></div>
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<h3 id="enums"><a class="doc-anchor" href="#enums">§</a>Enums</h3>
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<p>Deriving <code>Into</code> for enums is not supported as it would not always be successful,
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so <code>TryInto</code> should be used instead.</p>
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</div></details></section></div></main></body></html> |