| <!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="Creates a new future wrapping around a function returning [`Poll`]."><meta name="keywords" content="rust, rustlang, rust-lang, poll_fn"><title>poll_fn in futures::prelude::future - 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 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class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../../../futures/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="../../../futures/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a><div class="sidebar-elems"><h2><a href="index.html">In futures::prelude::future</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">Function <a href="../../index.html">futures</a>::<wbr><a href="../index.html">prelude</a>::<wbr><a href="index.html">future</a>::<wbr><a class="fn" href="#">poll_fn</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/futures_util/future/poll_fn.rs.html#36-38">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 fn"><code>pub fn poll_fn<T, F>(f: F) -> <a class="struct" href="../../future/struct.PollFn.html" title="struct futures::future::PollFn">PollFn</a><F><span class="notable-traits"><span class="notable-traits-tooltip">ⓘ<span class="notable-traits-tooltiptext"><span class="docblock"><span class="notable">Notable traits for <a class="struct" href="../../future/struct.PollFn.html" title="struct futures::future::PollFn">PollFn</a><F></span><code class="content"><span class="where fmt-newline">impl<T, F> <a class="trait" href="../../future/trait.Future.html" title="trait futures::future::Future">Future</a> for <a class="struct" href="../../future/struct.PollFn.html" title="struct futures::future::PollFn">PollFn</a><F><span class="where fmt-newline">where<br> F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnMut.html" title="trait core::ops::function::FnMut">FnMut</a>(&mut <a class="struct" href="../../task/struct.Context.html" title="struct futures::task::Context">Context</a><'_>) -> <a class="enum" href="../../task/enum.Poll.html" title="enum futures::task::Poll">Poll</a><T>,</span></span><span class="where fmt-newline"> type <a href="../../future/trait.Future.html#associatedtype.Output" class="associatedtype">Output</a> = T;</span></code></span></span></span></span><span class="where fmt-newline">where<br> F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnMut.html" title="trait core::ops::function::FnMut">FnMut</a>(&mut <a class="struct" href="../../task/struct.Context.html" title="struct futures::task::Context">Context</a><'_>) -> <a class="enum" href="../../task/enum.Poll.html" title="enum futures::task::Poll">Poll</a><T>,</span></code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Creates a new future wrapping around a function returning <a href="../../task/enum.Poll.html" title="Poll"><code>Poll</code></a>.</p> |
| <p>Polling the returned future delegates to the wrapped function.</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>futures::future::poll_fn; |
| <span class="kw">use </span>futures::task::{Context, Poll}; |
| |
| <span class="kw">fn </span>read_line(_cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<String> { |
| Poll::Ready(<span class="string">"Hello, World!"</span>.into()) |
| } |
| |
| <span class="kw">let </span>read_future = poll_fn(read_line); |
| <span class="macro">assert_eq!</span>(read_future.<span class="kw">await</span>, <span class="string">"Hello, World!"</span>.to_owned());</code></pre></div> |
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