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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="Returns a new `FutureService` for the given future."><title>future_service in tower::util - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Italic-81dc35de.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-MediumItalic-ccf7e434.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2"href="../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../../static.files/rustdoc-ca0dd0c4.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="tower" data-themes="" data-resource-suffix="" data-rustdoc-version="1.93.1 (01f6ddf75 2026-02-11) (Arch Linux rust 1:1.93.1-1)" data-channel="1.93.1" data-search-js="search-9e2438ea.js" data-stringdex-js="stringdex-a3946164.js" data-settings-js="settings-c38705f0.js" ><script src="../../static.files/storage-e2aeef58.js"></script><script defer src="sidebar-items.js"></script><script defer src="../../static.files/main-a410ff4d.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-263c88ec.css"></noscript><link rel="alternate icon" type="image/png" href="../../static.files/favicon-32x32-eab170b8.png"><link rel="icon" type="image/svg+xml" href="../../static.files/favicon-044be391.svg"></head><body class="rustdoc fn"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><rustdoc-topbar><h2><a href="#">future_service</a></h2></rustdoc-topbar><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../../tower/index.html">tower</a><span class="version">0.5.3</span></h2></div><div class="sidebar-elems"><section id="rustdoc-toc"><h2 class="location"><a href="#">future_<wbr>service</a></h2><h3><a href="#">Sections</a></h3><ul class="block top-toc"><li><a href="#example" title="Example">Example</a></li><li><a href="#regarding-the-unpin-bound" title="Regarding the `Unpin` bound">Regarding the <code>Unpin</code> bound</a></li></ul></section><div id="rustdoc-modnav"><h2><a href="index.html">In tower::<wbr>util</a></h2></div></div></nav><div class="sidebar-resizer" title="Drag to resize sidebar"></div><main><div class="width-limiter"><section id="main-content" class="content"><div class="main-heading"><div class="rustdoc-breadcrumbs"><a href="../index.html">tower</a>::<wbr><a href="index.html">util</a></div><h1>Function <span class="fn">future_<wbr>service</span> <button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../../src/tower/util/future_service.rs.html#48-54">Source</a> </span></div><pre class="rust item-decl"><code>pub fn future_service<F, S, R, E>(future: F) -> <a class="struct" href="struct.FutureService.html" title="struct tower::util::FutureService">FutureService</a><F, S><div class="where">where
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F: <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/future/future/trait.Future.html" title="trait core::future::future::Future">Future</a><Output = <a class="enum" href="https://doc.rust-lang.org/1.93.1/core/result/enum.Result.html" title="enum core::result::Result">Result</a><S, E>> + <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Unpin.html" title="trait core::marker::Unpin">Unpin</a>,
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S: <a class="trait" href="../trait.Service.html" title="trait tower::Service">Service</a><R, Error = E>,</div></code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Returns a new <a href="struct.FutureService.html" title="struct tower::util::FutureService"><code>FutureService</code></a> for the given future.</p>
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<p>A <a href="struct.FutureService.html" title="struct tower::util::FutureService"><code>FutureService</code></a> allows you to treat a future that resolves to a service as a service. This
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can be useful for services that are created asynchronously.</p>
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<h2 id="example"><a class="doc-anchor" href="#example">§</a>Example</h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tower::{service_fn, Service, ServiceExt};
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<span class="kw">use </span>tower::util::future_service;
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<span class="kw">use </span>std::convert::Infallible;
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<span class="comment">// A future which outputs a type implementing `Service`.
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</span><span class="kw">let </span>future_of_a_service = <span class="kw">async </span>{
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<span class="kw">let </span>svc = service_fn(|_req: ()| <span class="kw">async </span>{ <span class="prelude-val">Ok</span>::<<span class="kw">_</span>, Infallible>(<span class="string">"ok"</span>) });
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<span class="prelude-val">Ok</span>::<<span class="kw">_</span>, Infallible>(svc)
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};
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<span class="comment">// Wrap the future with a `FutureService`, allowing it to be used
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// as a service without awaiting the future's completion:
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</span><span class="kw">let </span><span class="kw-2">mut </span>svc = future_service(Box::pin(future_of_a_service));
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<span class="comment">// Now, when we wait for the service to become ready, it will
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// drive the future to completion internally.
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</span><span class="kw">let </span>svc = svc.ready().<span class="kw">await</span>.unwrap();
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<span class="kw">let </span>res = svc.call(()).<span class="kw">await</span>.unwrap();</code></pre></div><h2 id="regarding-the-unpin-bound"><a class="doc-anchor" href="#regarding-the-unpin-bound">§</a>Regarding the <a href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Unpin.html" title="trait core::marker::Unpin"><code>Unpin</code></a> bound</h2>
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<p>The <a href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Unpin.html" title="trait core::marker::Unpin"><code>Unpin</code></a> bound on <code>F</code> is necessary because the future will be polled in
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<a href="../trait.Service.html#tymethod.poll_ready" title="method tower::Service::poll_ready"><code>Service::poll_ready</code></a> which doesn’t have a pinned receiver (it takes <code>&mut self</code> and not <code>self: Pin<&mut Self></code>). So we cannot put the future into a <code>Pin</code> without requiring <code>Unpin</code>.</p>
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<p>This will most likely come up if you’re calling <code>future_service</code> with an async block. In that
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case you can use <code>Box::pin(async { ... })</code> as shown in the example.</p>
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</div></details></section></div></main></body></html> |