| <!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 thread-safe cell that can be written to only once."><meta name="keywords" content="rust, rustlang, rust-lang, OnceCell"><title>OnceCell in tokio::sync - 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 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href="../../tokio/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../../tokio/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><h3><a href="#implementations">Methods</a></h3><ul class="block"><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.initialized">initialized</a></li><li><a href="#method.into_inner">into_inner</a></li><li><a href="#method.new">new</a></li><li><a href="#method.new_with">new_with</a></li><li><a href="#method.set">set</a></li><li><a href="#method.take">take</a></li></ul><h3><a href="#trait-implementations">Trait Implementations</a></h3><ul class="block"><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-Drop-for-OnceCell%3CT%3E">Drop</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-Send-for-OnceCell%3CT%3E">Send</a></li><li><a href="#impl-Sync-for-OnceCell%3CT%3E">Sync</a></li></ul><h3><a href="#synthetic-implementations">Auto Trait Implementations</a></h3><ul class="block"><li><a href="#impl-RefUnwindSafe-for-OnceCell%3CT%3E">!RefUnwindSafe</a></li><li><a href="#impl-Unpin-for-OnceCell%3CT%3E">Unpin</a></li><li><a href="#impl-UnwindSafe-for-OnceCell%3CT%3E">UnwindSafe</a></li></ul><h3><a href="#blanket-implementations">Blanket Implementations</a></h3><ul class="block"><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></section><h2><a href="index.html">In tokio::sync</a></h2></div></nav><main><div class="width-limiter"><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"><a href="../../help.html">?</a></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><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn">Struct <a href="../index.html">tokio</a>::<wbr><a href="index.html">sync</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></h1><span class="out-of-band"><a class="srclink" href="../../src/tokio/sync/once_cell.rs.html#70-74">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="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 thread-safe cell that can be written to only once.</p> |
| <p>A <code>OnceCell</code> is typically used for global variables that need to be |
| initialized once on first use, but need no further changes. The <code>OnceCell</code> |
| in Tokio allows the initialization procedure to be asynchronous.</p> |
| <h2 id="examples"><a href="#examples">Examples</a></h2> |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tokio::sync::OnceCell; |
| |
| <span class="kw">async fn </span>some_computation() -> u32 { |
| <span class="number">1 </span>+ <span class="number">1 |
| </span>} |
| |
| <span class="kw">static </span>ONCE: OnceCell<u32> = OnceCell::const_new(); |
| |
| <span class="attribute">#[tokio::main] |
| </span><span class="kw">async fn </span>main() { |
| <span class="kw">let </span>result = ONCE.get_or_init(some_computation).<span class="kw">await</span>; |
| <span class="macro">assert_eq!</span>(<span class="kw-2">*</span>result, <span class="number">2</span>); |
| }</code></pre></div> |
| <p>It is often useful to write a wrapper method for accessing the value.</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tokio::sync::OnceCell; |
| |
| <span class="kw">static </span>ONCE: OnceCell<u32> = OnceCell::const_new(); |
| |
| <span class="kw">async fn </span>get_global_integer() -> <span class="kw-2">&</span><span class="lifetime">'static </span>u32 { |
| ONCE.get_or_init(|| <span class="kw">async </span>{ |
| <span class="number">1 </span>+ <span class="number">1 |
| </span>}).<span class="kw">await |
| </span>} |
| |
| <span class="attribute">#[tokio::main] |
| </span><span class="kw">async fn </span>main() { |
| <span class="kw">let </span>result = get_global_integer().<span class="kw">await</span>; |
| <span class="macro">assert_eq!</span>(<span class="kw-2">*</span>result, <span class="number">2</span>); |
| }</code></pre></div> |
| </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"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#127-402">source</a><a href="#impl-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::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"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#129-135">source</a><h4 class="code-header">pub fn <a href="#method.new" class="fnname">new</a>() -> Self</h4></section></summary><div class="docblock"><p>Creates a new empty <code>OnceCell</code> instance.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.new_with" class="method has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#142-148">source</a><h4 class="code-header">pub fn <a href="#method.new_with" class="fnname">new_with</a>(value: Option<T>) -> Self</h4></section></summary><div class="docblock"><p>Creates a new <code>OnceCell</code> that contains the provided value, if any.</p> |
| <p>If the <code>Option</code> is <code>None</code>, this is equivalent to <code>OnceCell::new</code>.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.initialized" class="method has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#186-190">source</a><h4 class="code-header">pub fn <a href="#method.initialized" class="fnname">initialized</a>(&self) -> bool</h4></section></summary><div class="docblock"><p>Returns <code>true</code> if the <code>OnceCell</code> currently contains a value, and <code>false</code> |
| otherwise.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.get" class="method has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#226-232">source</a><h4 class="code-header">pub fn <a href="#method.get" class="fnname">get</a>(&self) -> Option<&T></h4></section></summary><div class="docblock"><p>Returns a reference to the value currently stored in the <code>OnceCell</code>, or |
| <code>None</code> if the <code>OnceCell</code> is empty.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.get_mut" class="method has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#240-246">source</a><h4 class="code-header">pub fn <a href="#method.get_mut" class="fnname">get_mut</a>(&mut self) -> Option<&mut T></h4></section></summary><div class="docblock"><p>Returns a mutable reference to the value currently stored in the |
| <code>OnceCell</code>, or <code>None</code> if the <code>OnceCell</code> is empty.</p> |
| <p>Since this call borrows the <code>OnceCell</code> mutably, it is safe to mutate the |
| value inside the <code>OnceCell</code> — the mutable borrow statically guarantees |
| no other references exist.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.set" class="method has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#259-284">source</a><h4 class="code-header">pub fn <a href="#method.set" class="fnname">set</a>(&self, value: T) -> Result<(), <a class="enum" href="enum.SetError.html" title="enum tokio::sync::SetError">SetError</a><T>></h4></section></summary><div class="docblock"><p>Sets the value of the <code>OnceCell</code> to the given value if the <code>OnceCell</code> is |
| empty.</p> |
| <p>If the <code>OnceCell</code> already has a value, this call will fail with an |
| <a href="enum.SetError.html#variant.AlreadyInitializedError"><code>SetError::AlreadyInitializedError</code></a>.</p> |
| <p>If the <code>OnceCell</code> is empty, but some other task is currently trying to |
| set the value, this call will fail with <a href="enum.SetError.html#variant.InitializingError"><code>SetError::InitializingError</code></a>.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.get_or_init" class="method has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#299-332">source</a><h4 class="code-header">pub async fn <a href="#method.get_or_init" class="fnname">get_or_init</a><F, Fut>(&self, f: F) -> &T<span class="where fmt-newline">where<br> F: FnOnce() -> Fut,<br> Fut: Future<Output = T>,</span></h4></section></summary><div class="docblock"><p>Gets the value currently in the <code>OnceCell</code>, or initialize it with the |
| given asynchronous operation.</p> |
| <p>If some other task is currently working on initializing the <code>OnceCell</code>, |
| this call will wait for that other task to finish, then return the value |
| that the other task produced.</p> |
| <p>If the provided operation is cancelled or panics, the initialization |
| attempt is cancelled. If there are other tasks waiting for the value to |
| be initialized, one of them will start another attempt at initializing |
| the value.</p> |
| <p>This will deadlock if <code>f</code> tries to initialize the cell recursively.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.get_or_try_init" class="method has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#347-383">source</a><h4 class="code-header">pub async fn <a href="#method.get_or_try_init" class="fnname">get_or_try_init</a><E, F, Fut>(&self, f: F) -> Result<&T, E><span class="where fmt-newline">where<br> F: FnOnce() -> Fut,<br> Fut: Future<Output = Result<T, E>>,</span></h4></section></summary><div class="docblock"><p>Gets the value currently in the <code>OnceCell</code>, or initialize it with the |
| given asynchronous operation.</p> |
| <p>If some other task is currently working on initializing the <code>OnceCell</code>, |
| this call will wait for that other task to finish, then return the value |
| that the other task produced.</p> |
| <p>If the provided operation returns an error, is cancelled or panics, the |
| initialization attempt is cancelled. If there are other tasks waiting |
| for the value to be initialized, one of them will start another attempt |
| at initializing the value.</p> |
| <p>This will deadlock if <code>f</code> tries to initialize the cell recursively.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.into_inner" class="method has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#387-395">source</a><h4 class="code-header">pub fn <a href="#method.into_inner" class="fnname">into_inner</a>(self) -> Option<T></h4></section></summary><div class="docblock"><p>Takes the value from the cell, destroying the cell in the process. |
| Returns <code>None</code> if the cell is empty.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.take" class="method has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#399-401">source</a><h4 class="code-header">pub fn <a href="#method.take" class="fnname">take</a>(&mut self) -> Option<T></h4></section></summary><div class="docblock"><p>Takes ownership of the current value, leaving the cell empty. Returns |
| <code>None</code> if the cell is empty.</p> |
| </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"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#90-94">source</a><a href="#impl-Clone-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T: Clone> Clone for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::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"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#91-93">source</a><a href="#method.clone" class="anchor"></a><h4 class="code-header">fn <a class="fnname">clone</a>(&self) -> <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::OnceCell">OnceCell</a><T></h4></section></summary><div class='docblock'>Returns a copy of the value. <a>Read more</a></div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.clone_from" class="method trait-impl has-srclink"><span class="since rightside" title="Stable since Rust version 1.0.0">1.0.0</span><a href="#method.clone_from" class="anchor"></a><h4 class="code-header">const fn <a class="fnname">clone_from</a>(&mut self, source: &Self)</h4></section></summary><div class='docblock'>Performs copy-assignment from <code>source</code>. <a>Read more</a></div></details></div></details><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-Debug-for-OnceCell%3CT%3E" class="impl has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#82-88">source</a><a href="#impl-Debug-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T: Debug> Debug for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::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"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#83-87">source</a><a href="#method.fmt" class="anchor"></a><h4 class="code-header">fn <a class="fnname">fmt</a>(&self, fmt: &mut Formatter<'_>) -> Result</h4></section></summary><div class='docblock'>Formats the value using the given formatter. <a>Read more</a></div></details></div></details><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-Default-for-OnceCell%3CT%3E" class="impl has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#76-80">source</a><a href="#impl-Default-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> Default for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::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"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#77-79">source</a><a href="#method.default" class="anchor"></a><h4 class="code-header">fn <a class="fnname">default</a>() -> <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::OnceCell">OnceCell</a><T></h4></section></summary><div class='docblock'>Returns the “default value” for a type. <a>Read more</a></div></details></div></details><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-Drop-for-OnceCell%3CT%3E" class="impl has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#104-113">source</a><a href="#impl-Drop-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> Drop for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::OnceCell">OnceCell</a><T></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.drop" class="method trait-impl has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#105-112">source</a><a href="#method.drop" class="anchor"></a><h4 class="code-header">fn <a class="fnname">drop</a>(&mut self)</h4></section></summary><div class='docblock'>Executes the destructor for this type. <a>Read more</a></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"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#115-125">source</a><a href="#impl-From%3CT%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> From<T> for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::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"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#116-124">source</a><a href="#method.from" class="anchor"></a><h4 class="code-header">fn <a class="fnname">from</a>(value: T) -> Self</h4></section></summary><div class='docblock'>Converts to this type from the input type.</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"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#96-100">source</a><a href="#impl-PartialEq%3COnceCell%3CT%3E%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T: PartialEq> PartialEq<<a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::OnceCell">OnceCell</a><T>> for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::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"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#97-99">source</a><a href="#method.eq" class="anchor"></a><h4 class="code-header">fn <a class="fnname">eq</a>(&self, other: &<a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::OnceCell">OnceCell</a><T>) -> bool</h4></section></summary><div class='docblock'>This method tests for <code>self</code> and <code>other</code> values to be equal, and is used |
| by <code>==</code>. <a>Read more</a></div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.ne" class="method trait-impl has-srclink"><span class="since rightside" title="Stable since Rust version 1.0.0">1.0.0</span><a href="#method.ne" class="anchor"></a><h4 class="code-header">const fn <a class="fnname">ne</a>(&self, other: &Rhs) -> bool</h4></section></summary><div class='docblock'>This method tests for <code>!=</code>. The default implementation is almost always |
| sufficient, and should not be overridden without very good reason. <a>Read more</a></div></details></div></details><section id="impl-Eq-for-OnceCell%3CT%3E" class="impl has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#102">source</a><a href="#impl-Eq-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T: Eq> Eq for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::OnceCell">OnceCell</a><T></h3></section><section id="impl-Send-for-OnceCell%3CT%3E" class="impl has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#414">source</a><a href="#impl-Send-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T: Send> Send for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::OnceCell">OnceCell</a><T></h3></section><section id="impl-Sync-for-OnceCell%3CT%3E" class="impl has-srclink"><a class="srclink rightside" href="../../src/tokio/sync/once_cell.rs.html#409">source</a><a href="#impl-Sync-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T: Sync + Send> Sync for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::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-RefUnwindSafe-for-OnceCell%3CT%3E" class="impl has-srclink"><a href="#impl-RefUnwindSafe-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> !RefUnwindSafe for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::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">impl<T> Unpin for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::OnceCell">OnceCell</a><T><span class="where fmt-newline">where<br> T: Unpin,</span></h3></section><section id="impl-UnwindSafe-for-OnceCell%3CT%3E" class="impl has-srclink"><a href="#impl-UnwindSafe-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> UnwindSafe for <a class="struct" href="struct.OnceCell.html" title="struct tokio::sync::OnceCell">OnceCell</a><T><span class="where fmt-newline">where<br> T: UnwindSafe,</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"><a href="#impl-Any-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> Any for T<span class="where fmt-newline">where<br> T: 'static + ?Sized,</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"><a href="#method.type_id" class="anchor"></a><h4 class="code-header">fn <a class="fnname">type_id</a>(&self) -> TypeId</h4></section></summary><div class='docblock'>Gets the <code>TypeId</code> of <code>self</code>. <a>Read more</a></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"><a href="#impl-Borrow%3CT%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> Borrow<T> for T<span class="where fmt-newline">where<br> T: ?Sized,</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="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/91522" title="Tracking issue for const_borrow">unstable</a></span><a href="#method.borrow" class="anchor"></a><h4 class="code-header">fn <a class="fnname">borrow</a>(&self) -> &T</h4></section></summary><div class='docblock'>Immutably borrows from an owned value. <a>Read more</a></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"><a href="#impl-BorrowMut%3CT%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> BorrowMut<T> for T<span class="where fmt-newline">where<br> T: ?Sized,</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="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/91522" title="Tracking issue for const_borrow">unstable</a></span><a href="#method.borrow_mut" class="anchor"></a><h4 class="code-header">fn <a class="fnname">borrow_mut</a>(&mut self) -> &mut T</h4></section></summary><div class='docblock'>Mutably borrows from an owned value. <a>Read more</a></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"><a href="#impl-From%3C!%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> From<!> 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="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span><a href="#method.from-2" class="anchor"></a><h4 class="code-header">fn <a class="fnname">from</a>(t: !) -> T</h4></section></summary><div class='docblock'>Converts to this type from the input type.</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"><a href="#impl-From%3CT%3E-for-OnceCell%3CT%3E-1" class="anchor"></a><h3 class="code-header">impl<T> From<T> 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="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span><a href="#method.from-1" class="anchor"></a><h4 class="code-header">fn <a class="fnname">from</a>(t: T) -> T</h4></section></summary><div class="docblock"><p>Returns the argument unchanged.</p> |
| </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"><a href="#impl-Into%3CU%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T, U> Into<U> for T<span class="where fmt-newline">where<br> U: From<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="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span><a href="#method.into" class="anchor"></a><h4 class="code-header">fn <a class="fnname">into</a>(self) -> U</h4></section></summary><div class="docblock"><p>Calls <code>U::from(self)</code>.</p> |
| <p>That is, this conversion is whatever the implementation of |
| <code>[From]<T> for U</code> chooses to do.</p> |
| </div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-ToOwned-for-OnceCell%3CT%3E" class="impl has-srclink"><a href="#impl-ToOwned-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> ToOwned for T<span class="where fmt-newline">where<br> T: Clone,</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 class="associatedtype">Owned</a> = T</h4></section></summary><div class='docblock'>The resulting type after obtaining ownership.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.to_owned" class="method trait-impl has-srclink"><a href="#method.to_owned" class="anchor"></a><h4 class="code-header">fn <a class="fnname">to_owned</a>(&self) -> T</h4></section></summary><div class='docblock'>Creates owned data from borrowed data, usually by cloning. <a>Read more</a></div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.clone_into" class="method trait-impl has-srclink"><a href="#method.clone_into" class="anchor"></a><h4 class="code-header">fn <a class="fnname">clone_into</a>(&self, target: &mut T)</h4></section></summary><div class='docblock'>Uses borrowed data to replace owned data, usually by cloning. <a>Read more</a></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"><a href="#impl-TryFrom%3CU%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T, U> TryFrom<U> for T<span class="where fmt-newline">where<br> U: Into<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 class="associatedtype">Error</a> = Infallible</h4></section></summary><div class='docblock'>The type returned in the event of a conversion error.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.try_from" class="method trait-impl has-srclink"><span class="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span><a href="#method.try_from" class="anchor"></a><h4 class="code-header">fn <a class="fnname">try_from</a>(value: U) -> Result<T, <T as TryFrom<U>>::Error></h4></section></summary><div class='docblock'>Performs the conversion.</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"><a href="#impl-TryInto%3CU%3E-for-OnceCell%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T, U> TryInto<U> for T<span class="where fmt-newline">where<br> U: TryFrom<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 class="associatedtype">Error</a> = <U as TryFrom<T>>::Error</h4></section></summary><div class='docblock'>The type returned in the event of a conversion error.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.try_into" class="method trait-impl has-srclink"><span class="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span><a href="#method.try_into" class="anchor"></a><h4 class="code-header">fn <a class="fnname">try_into</a>(self) -> Result<U, <U as TryFrom<T>>::Error></h4></section></summary><div class='docblock'>Performs the conversion.</div></details></div></details></div></section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="tokio" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
