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<h1 class='fqn'><span class='in-band'>Function <a href='../../index.html'>tokio</a>::<wbr><a href='../index.html'>prelude</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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<pre class='rust fn'>pub fn lazy<F, R>(f: F) -> <a class="struct" href="../../../tokio/prelude/future/struct.Lazy.html" title="struct tokio::prelude::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="../../../tokio/prelude/trait.IntoFuture.html" title="trait tokio::prelude::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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<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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