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144 lines
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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 cell which can be written to only once. It is not thread safe."><meta name="keywords" content="rust, rustlang, rust-lang, OnceCell"><title>OnceCell in once_cell::unsync - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><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="../../ayu.css" disabled><link rel="stylesheet" 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class="location"></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../../once_cell/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a><h2 class="location"><a href="#">OnceCell</a></h2><div class="sidebar-elems"><section><div class="block"><h3 class="sidebar-title"><a href="#implementations">Methods</a></h3><ul><li><a href="#method.get">get</a></li><li><a href="#method.get_mut">get_mut</a></li><li><a href="#method.get_or_init">get_or_init</a></li><li><a href="#method.get_or_try_init">get_or_try_init</a></li><li><a href="#method.into_inner">into_inner</a></li><li><a href="#method.new">new</a></li><li><a href="#method.set">set</a></li><li><a href="#method.take">take</a></li><li><a href="#method.try_insert">try_insert</a></li><li><a href="#method.with_value">with_value</a></li></ul></div><div class="block"><h3 class="sidebar-title"><a href="#trait-implementations">Trait Implementations</a></h3><ul><li><a href="#impl-Clone-for-OnceCell%3CT%3E">Clone</a></li><li><a href="#impl-Debug-for-OnceCell%3CT%3E">Debug</a></li><li><a href="#impl-Default-for-OnceCell%3CT%3E">Default</a></li><li><a href="#impl-Eq-for-OnceCell%3CT%3E">Eq</a></li><li><a href="#impl-From%3CT%3E-for-OnceCell%3CT%3E">From<T></a></li><li><a href="#impl-PartialEq%3COnceCell%3CT%3E%3E-for-OnceCell%3CT%3E">PartialEq<OnceCell<T>></a></li><li><a href="#impl-RefUnwindSafe-for-OnceCell%3CT%3E">RefUnwindSafe</a></li><li><a href="#impl-UnwindSafe-for-OnceCell%3CT%3E">UnwindSafe</a></li></ul></div><div class="block"><h3 class="sidebar-title"><a href="#synthetic-implementations">Auto Trait Implementations</a></h3><ul><li><a href="#impl-Send-for-OnceCell%3CT%3E">Send</a></li><li><a href="#impl-Sync-for-OnceCell%3CT%3E">!Sync</a></li><li><a href="#impl-Unpin-for-OnceCell%3CT%3E">Unpin</a></li></ul></div><div class="block"><h3 class="sidebar-title"><a href="#blanket-implementations">Blanket Implementations</a></h3><ul><li><a href="#impl-Any-for-OnceCell%3CT%3E">Any</a></li><li><a href="#impl-Borrow%3CT%3E-for-OnceCell%3CT%3E">Borrow<T></a></li><li><a href="#impl-BorrowMut%3CT%3E-for-OnceCell%3CT%3E">BorrowMut<T></a></li><li><a href="#impl-From%3C!%3E-for-OnceCell%3CT%3E">From<!></a></li><li><a href="#impl-From%3CT%3E-for-OnceCell%3CT%3E-1">From<T></a></li><li><a href="#impl-Into%3CU%3E-for-OnceCell%3CT%3E">Into<U></a></li><li><a href="#impl-ToOwned-for-OnceCell%3CT%3E">ToOwned</a></li><li><a href="#impl-TryFrom%3CU%3E-for-OnceCell%3CT%3E">TryFrom<U></a></li><li><a href="#impl-TryInto%3CU%3E-for-OnceCell%3CT%3E">TryInto<U></a></li></ul></div></section><h2 class="location"><a href="index.html">In once_cell::unsync</a></h2></div></nav><main><div class="width-limiter"><div class="sub-container"><a class="sub-logo-container" href="../../once_cell/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><nav class="sub"><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><button type="button">?</button></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav></div><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn"><span class="in-band">Struct <a href="../index.html">once_cell</a>::<wbr><a href="index.html">unsync</a>::<wbr><a class="struct" href="#">OnceCell</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../../clipboard.svg" width="19" height="18" alt="Copy item path"></button></span></h1><span class="out-of-band"><a class="srclink" href="../../src/once_cell/lib.rs.html#384-387">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="docblock item-decl"><pre class="rust struct"><code>pub struct OnceCell<T> { /* private fields */ }</code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>A cell which can be written to only once. It is not thread safe.</p>
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<p>Unlike <a href="https://doc.rust-lang.org/std/cell/struct.RefCell.html"><code>std::cell::RefCell</code></a>, a <code>OnceCell</code> provides simple <code>&</code>
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references to the contents.</p>
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<h2 id="example"><a href="#example">Example</a></h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">once_cell::unsync::OnceCell</span>;
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<span class="kw">let</span> <span class="ident">cell</span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();
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<span class="macro">assert!</span>(<span class="ident">cell</span>.<span class="ident">get</span>().<span class="ident">is_none</span>());
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<span class="kw">let</span> <span class="ident">value</span>: <span class="kw-2">&</span><span class="ident">String</span> <span class="op">=</span> <span class="ident">cell</span>.<span class="ident">get_or_init</span>(<span class="op">|</span><span class="op">|</span> {
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<span class="string">"Hello, World!"</span>.<span class="ident">to_string</span>()
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});
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<span class="macro">assert_eq!</span>(<span class="ident">value</span>, <span class="string">"Hello, World!"</span>);
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<span class="macro">assert!</span>(<span class="ident">cell</span>.<span class="ident">get</span>().<span class="ident">is_some</span>());</code></pre></div>
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</div></details><h2 id="implementations" class="small-section-header">Implementations<a href="#implementations" class="anchor"></a></h2><div id="implementations-list"><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#441-662">source</a></span><a href="#impl-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T> <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.new" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#443-445">source</a></span><h4 class="code-header">pub const fn <a href="#method.new" class="fnname">new</a>() -> <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h4></section></summary><div class="docblock"><p>Creates a new empty cell.</p>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.with_value" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#448-450">source</a></span><h4 class="code-header">pub const fn <a href="#method.with_value" class="fnname">with_value</a>(value: T) -> <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h4></section></summary><div class="docblock"><p>Creates a new initialized cell.</p>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.get" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#456-459">source</a></span><h4 class="code-header">pub fn <a href="#method.get" class="fnname">get</a>(&self) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/option/enum.Option.html" title="enum core::option::Option">Option</a><<a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&</a>T></h4></section></summary><div class="docblock"><p>Gets a reference to the underlying value.</p>
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<p>Returns <code>None</code> if the cell is empty.</p>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.get_mut" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#478-481">source</a></span><h4 class="code-header">pub fn <a href="#method.get_mut" class="fnname">get_mut</a>(&mut self) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/option/enum.Option.html" title="enum core::option::Option">Option</a><<a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&mut </a>T></h4></section></summary><div class="docblock"><p>Gets a mutable reference to the underlying value.</p>
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<p>Returns <code>None</code> if the cell is empty.</p>
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<p>This method is allowed to violate the invariant of writing to a <code>OnceCell</code>
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at most once because it requires <code>&mut</code> access to <code>self</code>. As with all
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interior mutability, <code>&mut</code> access permits arbitrary modification:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">once_cell::unsync::OnceCell</span>;
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cell</span>: <span class="ident">OnceCell</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();
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<span class="ident">cell</span>.<span class="ident">set</span>(<span class="number">92</span>).<span class="ident">unwrap</span>();
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<span class="kw-2">*</span><span class="ident">cell</span>.<span class="ident">get_mut</span>().<span class="ident">unwrap</span>() <span class="op">=</span> <span class="number">93</span>;
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<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">get</span>(), <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="number">93</span>));</code></pre></div>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.set" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#500-505">source</a></span><h4 class="code-header">pub fn <a href="#method.set" class="fnname">set</a>(&self, value: T) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.unit.html">()</a>, T></h4></section></summary><div class="docblock"><p>Sets the contents of this cell to <code>value</code>.</p>
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<p>Returns <code>Ok(())</code> if the cell was empty and <code>Err(value)</code> if it was
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full.</p>
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<h5 id="example-1"><a href="#example-1">Example</a></h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">once_cell::unsync::OnceCell</span>;
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<span class="kw">let</span> <span class="ident">cell</span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();
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<span class="macro">assert!</span>(<span class="ident">cell</span>.<span class="ident">get</span>().<span class="ident">is_none</span>());
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<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">set</span>(<span class="number">92</span>), <span class="prelude-val">Ok</span>(()));
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<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">set</span>(<span class="number">62</span>), <span class="prelude-val">Err</span>(<span class="number">62</span>));
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<span class="macro">assert!</span>(<span class="ident">cell</span>.<span class="ident">get</span>().<span class="ident">is_some</span>());</code></pre></div>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.try_insert" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#521-533">source</a></span><h4 class="code-header">pub fn <a href="#method.try_insert" class="fnname">try_insert</a>(&self, value: T) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&</a>T, (<a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&</a>T, T)></h4></section></summary><div class="docblock"><p>Like <a href="struct.OnceCell.html#method.set"><code>set</code></a>, but also returns a reference to the final cell value.</p>
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<h5 id="example-2"><a href="#example-2">Example</a></h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">once_cell::unsync::OnceCell</span>;
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<span class="kw">let</span> <span class="ident">cell</span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();
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<span class="macro">assert!</span>(<span class="ident">cell</span>.<span class="ident">get</span>().<span class="ident">is_none</span>());
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<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">try_insert</span>(<span class="number">92</span>), <span class="prelude-val">Ok</span>(<span class="kw-2">&</span><span class="number">92</span>));
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<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">try_insert</span>(<span class="number">62</span>), <span class="prelude-val">Err</span>((<span class="kw-2">&</span><span class="number">92</span>, <span class="number">62</span>)));
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<span class="macro">assert!</span>(<span class="ident">cell</span>.<span class="ident">get</span>().<span class="ident">is_some</span>());</code></pre></div>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.get_or_init" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#556-565">source</a></span><h4 class="code-header">pub fn <a href="#method.get_or_init" class="fnname">get_or_init</a><F>(&self, f: F) -> <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&</a>T <span class="where fmt-newline">where<br> F: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>() -> T, </span></h4></section></summary><div class="docblock"><p>Gets the contents of the cell, initializing it with <code>f</code>
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if the cell was empty.</p>
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<h5 id="panics"><a href="#panics">Panics</a></h5>
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<p>If <code>f</code> panics, the panic is propagated to the caller, and the cell
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remains uninitialized.</p>
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<p>It is an error to reentrantly initialize the cell from <code>f</code>. Doing
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so results in a panic.</p>
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<h5 id="example-3"><a href="#example-3">Example</a></h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">once_cell::unsync::OnceCell</span>;
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<span class="kw">let</span> <span class="ident">cell</span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();
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<span class="kw">let</span> <span class="ident">value</span> <span class="op">=</span> <span class="ident">cell</span>.<span class="ident">get_or_init</span>(<span class="op">|</span><span class="op">|</span> <span class="number">92</span>);
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<span class="macro">assert_eq!</span>(<span class="ident">value</span>, <span class="kw-2">&</span><span class="number">92</span>);
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<span class="kw">let</span> <span class="ident">value</span> <span class="op">=</span> <span class="ident">cell</span>.<span class="ident">get_or_init</span>(<span class="op">|</span><span class="op">|</span> <span class="macro">unreachable!</span>());
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<span class="macro">assert_eq!</span>(<span class="ident">value</span>, <span class="kw-2">&</span><span class="number">92</span>);</code></pre></div>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.get_or_try_init" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#592-606">source</a></span><h4 class="code-header">pub fn <a href="#method.get_or_try_init" class="fnname">get_or_try_init</a><F, E>(&self, f: F) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&</a>T, E> <span class="where fmt-newline">where<br> F: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>() -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, E>, </span></h4></section></summary><div class="docblock"><p>Gets the contents of the cell, initializing it with <code>f</code> if
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the cell was empty. If the cell was empty and <code>f</code> failed, an
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error is returned.</p>
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<h5 id="panics-1"><a href="#panics-1">Panics</a></h5>
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<p>If <code>f</code> panics, the panic is propagated to the caller, and the cell
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remains uninitialized.</p>
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<p>It is an error to reentrantly initialize the cell from <code>f</code>. Doing
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so results in a panic.</p>
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<h5 id="example-4"><a href="#example-4">Example</a></h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">once_cell::unsync::OnceCell</span>;
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<span class="kw">let</span> <span class="ident">cell</span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();
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<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">get_or_try_init</span>(<span class="op">|</span><span class="op">|</span> <span class="prelude-val">Err</span>(())), <span class="prelude-val">Err</span>(()));
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<span class="macro">assert!</span>(<span class="ident">cell</span>.<span class="ident">get</span>().<span class="ident">is_none</span>());
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<span class="kw">let</span> <span class="ident">value</span> <span class="op">=</span> <span class="ident">cell</span>.<span class="ident">get_or_try_init</span>(<span class="op">|</span><span class="op">|</span> -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">i32</span>, ()<span class="op">></span> {
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<span class="prelude-val">Ok</span>(<span class="number">92</span>)
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});
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<span class="macro">assert_eq!</span>(<span class="ident">value</span>, <span class="prelude-val">Ok</span>(<span class="kw-2">&</span><span class="number">92</span>));
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<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">get</span>(), <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="number">92</span>))</code></pre></div>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.take" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#637-639">source</a></span><h4 class="code-header">pub fn <a href="#method.take" class="fnname">take</a>(&mut self) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></h4></section></summary><div class="docblock"><p>Takes the value out of this <code>OnceCell</code>, moving it back to an uninitialized state.</p>
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<p>Has no effect and returns <code>None</code> if the <code>OnceCell</code> hasn’t been initialized.</p>
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<h5 id="examples"><a href="#examples">Examples</a></h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">once_cell::unsync::OnceCell</span>;
|
||
|
||
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cell</span>: <span class="ident">OnceCell</span><span class="op"><</span><span class="ident">String</span><span class="op">></span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();
|
||
<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">take</span>(), <span class="prelude-val">None</span>);
|
||
|
||
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cell</span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();
|
||
<span class="ident">cell</span>.<span class="ident">set</span>(<span class="string">"hello"</span>.<span class="ident">to_string</span>()).<span class="ident">unwrap</span>();
|
||
<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">take</span>(), <span class="prelude-val">Some</span>(<span class="string">"hello"</span>.<span class="ident">to_string</span>()));
|
||
<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">get</span>(), <span class="prelude-val">None</span>);</code></pre></div>
|
||
<p>This method is allowed to violate the invariant of writing to a <code>OnceCell</code>
|
||
at most once because it requires <code>&mut</code> access to <code>self</code>. As with all
|
||
interior mutability, <code>&mut</code> access permits arbitrary modification:</p>
|
||
|
||
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">once_cell::unsync::OnceCell</span>;
|
||
|
||
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cell</span>: <span class="ident">OnceCell</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();
|
||
<span class="ident">cell</span>.<span class="ident">set</span>(<span class="number">92</span>).<span class="ident">unwrap</span>();
|
||
<span class="ident">cell</span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();</code></pre></div>
|
||
</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.into_inner" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#657-661">source</a></span><h4 class="code-header">pub fn <a href="#method.into_inner" class="fnname">into_inner</a>(self) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/option/enum.Option.html" title="enum core::option::Option">Option</a><T></h4></section></summary><div class="docblock"><p>Consumes the <code>OnceCell</code>, returning the wrapped value.</p>
|
||
<p>Returns <code>None</code> if the cell was empty.</p>
|
||
<h5 id="examples-1"><a href="#examples-1">Examples</a></h5>
|
||
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">once_cell::unsync::OnceCell</span>;
|
||
|
||
<span class="kw">let</span> <span class="ident">cell</span>: <span class="ident">OnceCell</span><span class="op"><</span><span class="ident">String</span><span class="op">></span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();
|
||
<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">into_inner</span>(), <span class="prelude-val">None</span>);
|
||
|
||
<span class="kw">let</span> <span class="ident">cell</span> <span class="op">=</span> <span class="ident">OnceCell::new</span>();
|
||
<span class="ident">cell</span>.<span class="ident">set</span>(<span class="string">"hello"</span>.<span class="ident">to_string</span>()).<span class="ident">unwrap</span>();
|
||
<span class="macro">assert_eq!</span>(<span class="ident">cell</span>.<span class="ident">into_inner</span>(), <span class="prelude-val">Some</span>(<span class="string">"hello"</span>.<span class="ident">to_string</span>()));</code></pre></div>
|
||
</div></details></div></details></div><h2 id="trait-implementations" class="small-section-header">Trait Implementations<a href="#trait-implementations" class="anchor"></a></h2><div id="trait-implementations-list"><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-Clone-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#411-425">source</a></span><a href="#impl-Clone-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a>> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a> for <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.clone" class="method trait-impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#412-417">source</a></span><a href="#method.clone" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/clone/trait.Clone.html#tymethod.clone" class="fnname">clone</a>(&self) -> <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h4></section></summary><div class='docblock'><p>Returns a copy of the value. <a href="https://doc.rust-lang.org/1.64.0/core/clone/trait.Clone.html#tymethod.clone">Read more</a></p>
|
||
</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.clone_from" class="method trait-impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#419-424">source</a></span><a href="#method.clone_from" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/clone/trait.Clone.html#method.clone_from" class="fnname">clone_from</a>(&mut self, source: <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&</a>Self)</h4></section></summary><div class='docblock'><p>Performs copy-assignment from <code>source</code>. <a href="https://doc.rust-lang.org/1.64.0/core/clone/trait.Clone.html#method.clone_from">Read more</a></p>
|
||
</div></details></div></details><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-Debug-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#402-409">source</a></span><a href="#impl-Debug-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a>> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a> for <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.fmt" class="method trait-impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#403-408">source</a></span><a href="#method.fmt" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/fmt/trait.Debug.html#tymethod.fmt" class="fnname">fmt</a>(&self, f: &mut <a class="struct" href="https://doc.rust-lang.org/1.64.0/core/fmt/struct.Formatter.html" title="struct core::fmt::Formatter">Formatter</a><'_>) -> <a class="type" href="https://doc.rust-lang.org/1.64.0/core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></h4></section></summary><div class='docblock'><p>Formats the value using the given formatter. <a href="https://doc.rust-lang.org/1.64.0/core/fmt/trait.Debug.html#tymethod.fmt">Read more</a></p>
|
||
</div></details></div></details><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-Default-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#396-400">source</a></span><a href="#impl-Default-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/default/trait.Default.html" title="trait core::default::Default">Default</a> for <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.default" class="method trait-impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#397-399">source</a></span><a href="#method.default" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/default/trait.Default.html#tymethod.default" class="fnname">default</a>() -> Self</h4></section></summary><div class='docblock'><p>Returns the “default value” for a type. <a href="https://doc.rust-lang.org/1.64.0/core/default/trait.Default.html#tymethod.default">Read more</a></p>
|
||
</div></details></div></details><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-From%3CT%3E-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#435-439">source</a></span><a href="#impl-From%3CT%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html" title="trait core::convert::From">From</a><T> for <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.from" class="method trait-impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#436-438">source</a></span><a href="#method.from" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html#tymethod.from" class="fnname">from</a>(value: T) -> Self</h4></section></summary><div class='docblock'><p>Converts to this type from the input type.</p>
|
||
</div></details></div></details><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-PartialEq%3COnceCell%3CT%3E%3E-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#427-431">source</a></span><a href="#impl-PartialEq%3COnceCell%3CT%3E%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/cmp/trait.PartialEq.html" title="trait core::cmp::PartialEq">PartialEq</a>> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/cmp/trait.PartialEq.html" title="trait core::cmp::PartialEq">PartialEq</a><<a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T>> for <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.eq" class="method trait-impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#428-430">source</a></span><a href="#method.eq" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/cmp/trait.PartialEq.html#tymethod.eq" class="fnname">eq</a>(&self, other: <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&</a>Self) -> <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.bool.html">bool</a></h4></section></summary><div class='docblock'><p>This method tests for <code>self</code> and <code>other</code> values to be equal, and is used
|
||
by <code>==</code>. <a href="https://doc.rust-lang.org/1.64.0/core/cmp/trait.PartialEq.html#tymethod.eq">Read more</a></p>
|
||
</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.ne" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="Stable since Rust version 1.0.0">1.0.0</span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/cmp.rs.html#232">source</a></span><a href="#method.ne" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/cmp/trait.PartialEq.html#method.ne" class="fnname">ne</a>(&self, other: <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&</a>Rhs) -> <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.bool.html">bool</a></h4></section></summary><div class='docblock'><p>This method tests for <code>!=</code>.</p>
|
||
</div></details></div></details><section id="impl-Eq-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#433">source</a></span><a href="#impl-Eq-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/cmp/trait.Eq.html" title="trait core::cmp::Eq">Eq</a>> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/cmp/trait.Eq.html" title="trait core::cmp::Eq">Eq</a> for <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h3></section><section id="impl-RefUnwindSafe-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#393">source</a></span><a href="#impl-RefUnwindSafe-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/panic/unwind_safe/trait.RefUnwindSafe.html" title="trait core::panic::unwind_safe::RefUnwindSafe">RefUnwindSafe</a> + <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/panic/unwind_safe/trait.UnwindSafe.html" title="trait core::panic::unwind_safe::UnwindSafe">UnwindSafe</a>> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/panic/unwind_safe/trait.RefUnwindSafe.html" title="trait core::panic::unwind_safe::RefUnwindSafe">RefUnwindSafe</a> for <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h3></section><section id="impl-UnwindSafe-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/once_cell/lib.rs.html#394">source</a></span><a href="#impl-UnwindSafe-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/panic/unwind_safe/trait.UnwindSafe.html" title="trait core::panic::unwind_safe::UnwindSafe">UnwindSafe</a>> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/panic/unwind_safe/trait.UnwindSafe.html" title="trait core::panic::unwind_safe::UnwindSafe">UnwindSafe</a> for <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h3></section></div><h2 id="synthetic-implementations" class="small-section-header">Auto Trait Implementations<a href="#synthetic-implementations" class="anchor"></a></h2><div id="synthetic-implementations-list"><section id="impl-Send-for-OnceCell%3CT%3E" class="impl has-srclink"><a href="#impl-Send-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> for <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a>, </span></h3></section><section id="impl-Sync-for-OnceCell%3CT%3E" class="impl has-srclink"><a href="#impl-Sync-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T> !<a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Sync.html" title="trait core::marker::Sync">Sync</a> for <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T></h3></section><section id="impl-Unpin-for-OnceCell%3CT%3E" class="impl has-srclink"><a href="#impl-Unpin-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Unpin.html" title="trait core::marker::Unpin">Unpin</a> for <a class="struct" href="struct.OnceCell.html" title="struct once_cell::unsync::OnceCell">OnceCell</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Unpin.html" title="trait core::marker::Unpin">Unpin</a>, </span></h3></section></div><h2 id="blanket-implementations" class="small-section-header">Blanket Implementations<a href="#blanket-implementations" class="anchor"></a></h2><div id="blanket-implementations-list"><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-Any-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/any.rs.html#203">source</a></span><a href="#impl-Any-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/any/trait.Any.html" title="trait core::any::Any">Any</a> for T <span class="where fmt-newline">where<br> T: 'static + ?<a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.type_id" class="method trait-impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/any.rs.html#204">source</a></span><a href="#method.type_id" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/any/trait.Any.html#tymethod.type_id" class="fnname">type_id</a>(&self) -> <a class="struct" href="https://doc.rust-lang.org/1.64.0/core/any/struct.TypeId.html" title="struct core::any::TypeId">TypeId</a></h4></section></summary><div class='docblock'><p>Gets the <code>TypeId</code> of <code>self</code>. <a href="https://doc.rust-lang.org/1.64.0/core/any/trait.Any.html#tymethod.type_id">Read more</a></p>
|
||
</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-Borrow%3CT%3E-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/borrow.rs.html#209">source</a></span><a href="#impl-Borrow%3CT%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.Borrow.html" title="trait core::borrow::Borrow">Borrow</a><T> for T <span class="where fmt-newline">where<br> T: ?<a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.borrow" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/91522" title="Tracking issue for const_borrow">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/borrow.rs.html#211">source</a></span><a href="#method.borrow" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.Borrow.html#tymethod.borrow" class="fnname">borrow</a>(&self) -> <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&</a>T</h4></section></summary><div class='docblock'><p>Immutably borrows from an owned value. <a href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.Borrow.html#tymethod.borrow">Read more</a></p>
|
||
</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-BorrowMut%3CT%3E-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/borrow.rs.html#218">source</a></span><a href="#impl-BorrowMut%3CT%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.BorrowMut.html" title="trait core::borrow::BorrowMut">BorrowMut</a><T> for T <span class="where fmt-newline">where<br> T: ?<a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.borrow_mut" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/91522" title="Tracking issue for const_borrow">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/borrow.rs.html#219">source</a></span><a href="#method.borrow_mut" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.BorrowMut.html#tymethod.borrow_mut" class="fnname">borrow_mut</a>(&mut self) -> <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&mut </a>T</h4></section></summary><div class='docblock'><p>Mutably borrows from an owned value. <a href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.BorrowMut.html#tymethod.borrow_mut">Read more</a></p>
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</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-From%3C!%3E-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#574">source</a></span><a href="#impl-From%3C!%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html" title="trait core::convert::From">From</a><<a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.never.html">!</a>> for T</h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.from-1" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#575">source</a></span><a href="#method.from-1" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html#tymethod.from" class="fnname">from</a>(t: <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.never.html">!</a>) -> T</h4></section></summary><div class='docblock'><p>Converts to this type from the input type.</p>
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</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-From%3CT%3E-for-OnceCell%3CT%3E-1" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#557">source</a></span><a href="#impl-From%3CT%3E-for-OnceCell%3CT%3E-1" class="anchor"></a><h3 class="code-header in-band">impl<T> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html" title="trait core::convert::From">From</a><T> for T</h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.from-2" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#559">source</a></span><a href="#method.from-2" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html#tymethod.from" class="fnname">from</a>(t: T) -> T</h4></section></summary><div class="docblock"><p>Returns the argument unchanged.</p>
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</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-Into%3CU%3E-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#541">source</a></span><a href="#impl-Into%3CU%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T, U> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.Into.html" title="trait core::convert::Into">Into</a><U> for T <span class="where fmt-newline">where<br> U: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html" title="trait core::convert::From">From</a><T>, </span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.into" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#549">source</a></span><a href="#method.into" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.Into.html#tymethod.into" class="fnname">into</a>(self) -> U</h4></section></summary><div class="docblock"><p>Calls <code>U::from(self)</code>.</p>
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<p>That is, this conversion is whatever the implementation of
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<code><a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html" title="From">From</a><T> for U</code> chooses to do.</p>
|
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</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-ToOwned-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/alloc/borrow.rs.html#83">source</a></span><a href="#impl-ToOwned-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T> <a class="trait" href="https://doc.rust-lang.org/1.64.0/alloc/borrow/trait.ToOwned.html" title="trait alloc::borrow::ToOwned">ToOwned</a> for T <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a>, </span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle" open><summary><section id="associatedtype.Owned" class="associatedtype trait-impl has-srclink"><a href="#associatedtype.Owned" class="anchor"></a><h4 class="code-header">type <a href="https://doc.rust-lang.org/1.64.0/alloc/borrow/trait.ToOwned.html#associatedtype.Owned" class="associatedtype">Owned</a> = T</h4></section></summary><div class='docblock'><p>The resulting type after obtaining ownership.</p>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.to_owned" class="method trait-impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/alloc/borrow.rs.html#88">source</a></span><a href="#method.to_owned" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/alloc/borrow/trait.ToOwned.html#tymethod.to_owned" class="fnname">to_owned</a>(&self) -> T</h4></section></summary><div class='docblock'><p>Creates owned data from borrowed data, usually by cloning. <a href="https://doc.rust-lang.org/1.64.0/alloc/borrow/trait.ToOwned.html#tymethod.to_owned">Read more</a></p>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.clone_into" class="method trait-impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/alloc/borrow.rs.html#92">source</a></span><a href="#method.clone_into" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/alloc/borrow/trait.ToOwned.html#method.clone_into" class="fnname">clone_into</a>(&self, target: <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&mut </a>T)</h4></section></summary><div class='docblock'><p>Uses borrowed data to replace owned data, usually by cloning. <a href="https://doc.rust-lang.org/1.64.0/alloc/borrow/trait.ToOwned.html#method.clone_into">Read more</a></p>
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</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-TryFrom%3CU%3E-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#598">source</a></span><a href="#impl-TryFrom%3CU%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T, U> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a><U> for T <span class="where fmt-newline">where<br> U: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.Into.html" title="trait core::convert::Into">Into</a><T>, </span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle" open><summary><section id="associatedtype.Error" class="associatedtype trait-impl has-srclink"><a href="#associatedtype.Error" class="anchor"></a><h4 class="code-header">type <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html#associatedtype.Error" class="associatedtype">Error</a> = <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/convert/enum.Infallible.html" title="enum core::convert::Infallible">Infallible</a></h4></section></summary><div class='docblock'><p>The type returned in the event of a conversion error.</p>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.try_from" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#604">source</a></span><a href="#method.try_from" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html#tymethod.try_from" class="fnname">try_from</a>(value: U) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, <T as <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a><U>>::<a class="associatedtype" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a>></h4></section></summary><div class='docblock'><p>Performs the conversion.</p>
|
||
</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-TryInto%3CU%3E-for-OnceCell%3CT%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#583">source</a></span><a href="#impl-TryInto%3CU%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header in-band">impl<T, U> <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryInto.html" title="trait core::convert::TryInto">TryInto</a><U> for T <span class="where fmt-newline">where<br> U: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a><T>, </span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle" open><summary><section id="associatedtype.Error-1" class="associatedtype trait-impl has-srclink"><a href="#associatedtype.Error-1" class="anchor"></a><h4 class="code-header">type <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryInto.html#associatedtype.Error" class="associatedtype">Error</a> = <U as <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a><T>>::<a class="associatedtype" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a></h4></section></summary><div class='docblock'><p>The type returned in the event of a conversion error.</p>
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</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.try_into" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#589">source</a></span><a href="#method.try_into" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryInto.html#tymethod.try_into" class="fnname">try_into</a>(self) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><U, <U as <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a><T>>::<a class="associatedtype" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a>></h4></section></summary><div class='docblock'><p>Performs the conversion.</p>
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