| <!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="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/tower-layer-0.3.2/src/layer_fn.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>layer_fn.rs - source</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 rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../tower_layer/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../tower_layer/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><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="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="kw">use </span><span class="kw">super</span>::Layer; |
| <span class="kw">use </span>std::fmt; |
| |
| <span class="doccomment">/// Returns a new [`LayerFn`] that implements [`Layer`] by calling the |
| /// given function. |
| /// |
| /// The [`Layer::layer`] method takes a type implementing [`Service`] and |
| /// returns a different type implementing [`Service`]. In many cases, this can |
| /// be implemented by a function or a closure. The [`LayerFn`] helper allows |
| /// writing simple [`Layer`] implementations without needing the boilerplate of |
| /// a new struct implementing [`Layer`]. |
| /// |
| /// # Example |
| /// ```rust |
| /// # use tower::Service; |
| /// # use std::task::{Poll, Context}; |
| /// # use tower_layer::{Layer, layer_fn}; |
| /// # use std::fmt; |
| /// # use std::convert::Infallible; |
| /// # |
| /// // A middleware that logs requests before forwarding them to another service |
| /// pub struct LogService<S> { |
| /// target: &'static str, |
| /// service: S, |
| /// } |
| /// |
| /// impl<S, Request> Service<Request> for LogService<S> |
| /// where |
| /// S: Service<Request>, |
| /// Request: fmt::Debug, |
| /// { |
| /// type Response = S::Response; |
| /// type Error = S::Error; |
| /// type Future = S::Future; |
| /// |
| /// fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// self.service.poll_ready(cx) |
| /// } |
| /// |
| /// fn call(&mut self, request: Request) -> Self::Future { |
| /// // Log the request |
| /// println!("request = {:?}, target = {:?}", request, self.target); |
| /// |
| /// self.service.call(request) |
| /// } |
| /// } |
| /// |
| /// // A `Layer` that wraps services in `LogService` |
| /// let log_layer = layer_fn(|service| { |
| /// LogService { |
| /// service, |
| /// target: "tower-docs", |
| /// } |
| /// }); |
| /// |
| /// // An example service. This one uppercases strings |
| /// let uppercase_service = tower::service_fn(|request: String| async move { |
| /// Ok::<_, Infallible>(request.to_uppercase()) |
| /// }); |
| /// |
| /// // Wrap our service in a `LogService` so requests are logged. |
| /// let wrapped_service = log_layer.layer(uppercase_service); |
| /// ``` |
| /// |
| /// [`Service`]: https://docs.rs/tower-service/latest/tower_service/trait.Service.html |
| /// [`Layer::layer`]: crate::Layer::layer |
| </span><span class="kw">pub fn </span>layer_fn<T>(f: T) -> LayerFn<T> { |
| LayerFn { f } |
| } |
| |
| <span class="doccomment">/// A `Layer` implemented by a closure. See the docs for [`layer_fn`] for more details. |
| </span><span class="attribute">#[derive(Clone, Copy)] |
| </span><span class="kw">pub struct </span>LayerFn<F> { |
| f: F, |
| } |
| |
| <span class="kw">impl</span><F, S, Out> Layer<S> <span class="kw">for </span>LayerFn<F> |
| <span class="kw">where |
| </span>F: Fn(S) -> Out, |
| { |
| <span class="kw">type </span>Service = Out; |
| |
| <span class="kw">fn </span>layer(<span class="kw-2">&</span><span class="self">self</span>, inner: S) -> <span class="self">Self</span>::Service { |
| (<span class="self">self</span>.f)(inner) |
| } |
| } |
| |
| <span class="kw">impl</span><F> fmt::Debug <span class="kw">for </span>LayerFn<F> { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| f.debug_struct(<span class="string">"LayerFn"</span>) |
| .field(<span class="string">"f"</span>, <span class="kw-2">&</span><span class="macro">format_args!</span>(<span class="string">"{}"</span>, std::any::type_name::<F>())) |
| .finish() |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| |
| <span class="attribute">#[allow(dead_code)] |
| #[test] |
| </span><span class="kw">fn </span>layer_fn_has_useful_debug_impl() { |
| <span class="kw">struct </span>WrappedService<S> { |
| inner: S, |
| } |
| <span class="kw">let </span>layer = layer_fn(|svc| WrappedService { inner: svc }); |
| <span class="kw">let </span>_svc = layer.layer(<span class="string">"foo"</span>); |
| |
| <span class="macro">assert_eq!</span>( |
| <span class="string">"LayerFn { f: tower_layer::layer_fn::tests::layer_fn_has_useful_debug_impl::{{closure}} }"</span>.to_string(), |
| <span class="macro">format!</span>(<span class="string">"{:?}"</span>, layer), |
| ); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="tower_layer" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
