142 lines
6.6 KiB
HTML
142 lines
6.6 KiB
HTML
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<!DOCTYPE html>
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<html lang="en">
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<meta name="generator" content="rustdoc">
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<meta name="description" content="API documentation for the Rust `lazy` fn in crate `futures`.">
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<meta name="keywords" content="rust, rustlang, rust-lang, lazy">
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<title>futures::future::lazy - Rust</title>
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<link rel="stylesheet" type="text/css" href="../../normalize.css">
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<link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle">
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<body class="rustdoc fn">
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This old browser is unsupported and will most likely display funky
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things.
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<![endif]-->
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<div class="sidebar-menu">☰</div>
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<p class='location'><a href='../index.html'>futures</a>::<wbr><a href='index.html'>future</a></p><script>window.sidebarCurrent = {name: 'lazy', ty: 'fn', relpath: ''};</script><script defer src="sidebar-items.js"></script>
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autocomplete="off"
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placeholder="Click or press ‘S’ to search, ‘?’ for more options…"
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type="search">
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</form>
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</nav>
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<section id='main' class="content">
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<h1 class='fqn'><span class='in-band'>Function <a href='../index.html'>futures</a>::<wbr><a href='index.html'>future</a>::<wbr><a class="fn" href=''>lazy</a></span><span class='out-of-band'><span id='render-detail'>
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[<span class='inner'>−</span>]
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</a>
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</span><a class='srclink' href='../../src/futures/future/lazy.rs.html#44-51' title='goto source code'>[src]</a></span></h1>
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<pre class='rust fn'>pub fn lazy<F, R>(f: F) -> <a class="struct" href="../../futures/future/struct.Lazy.html" title="struct futures::future::Lazy">Lazy</a><F, R> <span class="where fmt-newline">where<br> F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>() -> R,<br> R: <a class="trait" href="../../futures/future/trait.IntoFuture.html" title="trait futures::future::IntoFuture">IntoFuture</a>, </span></pre><div class='docblock'><p>Creates a new future which will eventually be the same as the one created
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by the closure provided.</p>
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<p>The provided closure is only run once the future has a callback scheduled
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on it, otherwise the callback never runs. Once run, however, this future is
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the same as the one the closure creates.</p>
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<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
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<pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">futures</span>::<span class="ident">future</span>::<span class="kw-2">*</span>;
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<span class="kw">let</span> <span class="ident">a</span> <span class="op">=</span> <span class="ident">lazy</span>(<span class="op">||</span> <span class="ident">ok</span>::<span class="op"><</span><span class="ident">u32</span>, <span class="ident">u32</span><span class="op">></span>(<span class="number">1</span>));
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<span class="kw">let</span> <span class="ident">b</span> <span class="op">=</span> <span class="ident">lazy</span>(<span class="op">||</span> <span class="op">-></span> <span class="ident">FutureResult</span><span class="op"><</span><span class="ident">u32</span>, <span class="ident">u32</span><span class="op">></span> {
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<span class="macro">panic</span><span class="macro">!</span>(<span class="string">"oh no!"</span>)
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});
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<span class="ident">drop</span>(<span class="ident">b</span>); <span class="comment">// closure is never run</span></pre>
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</div></section>
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<h1 class="hidden">Help</h1>
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<div class="shortcuts">
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<h2>Keyboard Shortcuts</h2>
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<div class="infos">
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<h2>Search Tricks</h2>
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Prefix searches with a type followed by a colon (e.g.
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<code>fn:</code>) to restrict the search to a given type.
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Accepted types are: <code>fn</code>, <code>mod</code>,
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and <code>const</code>.
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</p>
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<p>
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Search functions by type signature (e.g.
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