| <!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-0.4.13/src/util/mod.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>mod.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/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/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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| <span id="1076">1076</span> |
| <span id="1077">1077</span> |
| <span id="1078">1078</span> |
| <span id="1079">1079</span> |
| <span id="1080">1080</span> |
| <span id="1081">1081</span> |
| <span id="1082">1082</span> |
| <span id="1083">1083</span> |
| </pre><pre class="rust"><code><span class="doccomment">//! Various utility types and functions that are generally used with Tower. |
| |
| </span><span class="kw">mod </span>and_then; |
| <span class="kw">mod </span>boxed; |
| <span class="kw">mod </span>boxed_clone; |
| <span class="kw">mod </span>call_all; |
| <span class="kw">mod </span>either; |
| |
| <span class="kw">mod </span>future_service; |
| <span class="kw">mod </span>map_err; |
| <span class="kw">mod </span>map_request; |
| <span class="kw">mod </span>map_response; |
| <span class="kw">mod </span>map_result; |
| |
| <span class="kw">mod </span>map_future; |
| <span class="kw">mod </span>oneshot; |
| <span class="kw">mod </span>optional; |
| <span class="kw">mod </span>ready; |
| <span class="kw">mod </span>service_fn; |
| <span class="kw">mod </span>then; |
| |
| <span class="attribute">#[allow(deprecated)] |
| </span><span class="kw">pub use </span><span class="self">self</span>::{ |
| and_then::{AndThen, AndThenLayer}, |
| boxed::{BoxLayer, BoxService, UnsyncBoxService}, |
| boxed_clone::BoxCloneService, |
| either::Either, |
| future_service::{future_service, FutureService}, |
| map_err::{MapErr, MapErrLayer}, |
| map_future::{MapFuture, MapFutureLayer}, |
| map_request::{MapRequest, MapRequestLayer}, |
| map_response::{MapResponse, MapResponseLayer}, |
| map_result::{MapResult, MapResultLayer}, |
| oneshot::Oneshot, |
| optional::Optional, |
| ready::{Ready, ReadyAnd, ReadyOneshot}, |
| service_fn::{service_fn, ServiceFn}, |
| then::{Then, ThenLayer}, |
| }; |
| |
| <span class="kw">pub use </span><span class="self">self</span>::call_all::{CallAll, CallAllUnordered}; |
| <span class="kw">use </span>std::future::Future; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::layer::util::Identity; |
| |
| <span class="kw">pub mod </span>error { |
| <span class="doccomment">//! Error types |
| |
| </span><span class="kw">pub use </span><span class="kw">super</span>::optional::error <span class="kw">as </span>optional; |
| } |
| |
| <span class="kw">pub mod </span>future { |
| <span class="doccomment">//! Future types |
| |
| </span><span class="kw">pub use </span><span class="kw">super</span>::and_then::AndThenFuture; |
| <span class="kw">pub use </span><span class="kw">super</span>::map_err::MapErrFuture; |
| <span class="kw">pub use </span><span class="kw">super</span>::map_response::MapResponseFuture; |
| <span class="kw">pub use </span><span class="kw">super</span>::map_result::MapResultFuture; |
| <span class="kw">pub use </span><span class="kw">super</span>::optional::future <span class="kw">as </span>optional; |
| <span class="kw">pub use </span><span class="kw">super</span>::then::ThenFuture; |
| } |
| |
| <span class="doccomment">/// An extension trait for `Service`s that provides a variety of convenient |
| /// adapters |
| </span><span class="kw">pub trait </span>ServiceExt<Request>: tower_service::Service<Request> { |
| <span class="doccomment">/// Yields a mutable reference to the service when it is ready to accept a request. |
| </span><span class="kw">fn </span>ready(<span class="kw-2">&mut </span><span class="self">self</span>) -> Ready<<span class="lifetime">'_</span>, <span class="self">Self</span>, Request> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| { |
| Ready::new(<span class="self">self</span>) |
| } |
| |
| <span class="doccomment">/// Yields a mutable reference to the service when it is ready to accept a request. |
| </span><span class="attribute">#[deprecated( |
| since = <span class="string">"0.4.6"</span>, |
| note = <span class="string">"please use the `ServiceExt::ready` method instead" |
| </span>)] |
| #[allow(deprecated)] |
| </span><span class="kw">fn </span>ready_and(<span class="kw-2">&mut </span><span class="self">self</span>) -> ReadyAnd<<span class="lifetime">'_</span>, <span class="self">Self</span>, Request> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| { |
| ReadyAnd::new(<span class="self">self</span>) |
| } |
| |
| <span class="doccomment">/// Yields the service when it is ready to accept a request. |
| </span><span class="kw">fn </span>ready_oneshot(<span class="self">self</span>) -> ReadyOneshot<<span class="self">Self</span>, Request> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| { |
| ReadyOneshot::new(<span class="self">self</span>) |
| } |
| |
| <span class="doccomment">/// Consume this `Service`, calling with the providing request once it is ready. |
| </span><span class="kw">fn </span>oneshot(<span class="self">self</span>, req: Request) -> Oneshot<<span class="self">Self</span>, Request> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| { |
| Oneshot::new(<span class="self">self</span>, req) |
| } |
| |
| <span class="doccomment">/// Process all requests from the given [`Stream`], and produce a [`Stream`] of their responses. |
| /// |
| /// This is essentially [`Stream<Item = Request>`][stream] + `Self` => [`Stream<Item = |
| /// Response>`][stream]. See the documentation for [`CallAll`] for |
| /// details. |
| /// |
| /// [`Stream`]: https://docs.rs/futures/latest/futures/stream/trait.Stream.html |
| /// [stream]: https://docs.rs/futures/latest/futures/stream/trait.Stream.html |
| </span><span class="kw">fn </span>call_all<S>(<span class="self">self</span>, reqs: S) -> CallAll<<span class="self">Self</span>, S> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| <span class="self">Self</span>::Error: Into<<span class="kw">crate</span>::BoxError>, |
| S: futures_core::Stream<Item = Request>, |
| { |
| CallAll::new(<span class="self">self</span>, reqs) |
| } |
| |
| <span class="doccomment">/// Executes a new future after this service's future resolves. This does |
| /// not alter the behaviour of the [`poll_ready`] method. |
| /// |
| /// This method can be used to change the [`Response`] type of the service |
| /// into a different type. You can use this method to chain along a computation once the |
| /// service's response has been resolved. |
| /// |
| /// [`Response`]: crate::Service::Response |
| /// [`poll_ready`]: crate::Service::poll_ready |
| /// |
| /// # Example |
| /// ``` |
| /// # use std::task::{Poll, Context}; |
| /// # use tower::{Service, ServiceExt}; |
| /// # |
| /// # struct DatabaseService; |
| /// # impl DatabaseService { |
| /// # fn new(address: &str) -> Self { |
| /// # DatabaseService |
| /// # } |
| /// # } |
| /// # |
| /// # struct Record { |
| /// # pub name: String, |
| /// # pub age: u16 |
| /// # } |
| /// # |
| /// # impl Service<u32> for DatabaseService { |
| /// # type Response = Record; |
| /// # type Error = u8; |
| /// # type Future = futures_util::future::Ready<Result<Record, u8>>; |
| /// # |
| /// # fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// # Poll::Ready(Ok(())) |
| /// # } |
| /// # |
| /// # fn call(&mut self, request: u32) -> Self::Future { |
| /// # futures_util::future::ready(Ok(Record { name: "Jack".into(), age: 32 })) |
| /// # } |
| /// # } |
| /// # |
| /// # async fn avatar_lookup(name: String) -> Result<Vec<u8>, u8> { Ok(vec![]) } |
| /// # |
| /// # fn main() { |
| /// # async { |
| /// // A service returning Result<Record, _> |
| /// let service = DatabaseService::new("127.0.0.1:8080"); |
| /// |
| /// // Map the response into a new response |
| /// let mut new_service = service.and_then(|record: Record| async move { |
| /// let name = record.name; |
| /// avatar_lookup(name).await |
| /// }); |
| /// |
| /// // Call the new service |
| /// let id = 13; |
| /// let avatar = new_service.call(id).await.unwrap(); |
| /// # }; |
| /// # } |
| /// ``` |
| </span><span class="kw">fn </span>and_then<F>(<span class="self">self</span>, f: F) -> AndThen<<span class="self">Self</span>, F> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| F: Clone, |
| { |
| AndThen::new(<span class="self">self</span>, f) |
| } |
| |
| <span class="doccomment">/// Maps this service's response value to a different value. This does not |
| /// alter the behaviour of the [`poll_ready`] method. |
| /// |
| /// This method can be used to change the [`Response`] type of the service |
| /// into a different type. It is similar to the [`Result::map`] |
| /// method. You can use this method to chain along a computation once the |
| /// service's response has been resolved. |
| /// |
| /// [`Response`]: crate::Service::Response |
| /// [`poll_ready`]: crate::Service::poll_ready |
| /// |
| /// # Example |
| /// ``` |
| /// # use std::task::{Poll, Context}; |
| /// # use tower::{Service, ServiceExt}; |
| /// # |
| /// # struct DatabaseService; |
| /// # impl DatabaseService { |
| /// # fn new(address: &str) -> Self { |
| /// # DatabaseService |
| /// # } |
| /// # } |
| /// # |
| /// # struct Record { |
| /// # pub name: String, |
| /// # pub age: u16 |
| /// # } |
| /// # |
| /// # impl Service<u32> for DatabaseService { |
| /// # type Response = Record; |
| /// # type Error = u8; |
| /// # type Future = futures_util::future::Ready<Result<Record, u8>>; |
| /// # |
| /// # fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// # Poll::Ready(Ok(())) |
| /// # } |
| /// # |
| /// # fn call(&mut self, request: u32) -> Self::Future { |
| /// # futures_util::future::ready(Ok(Record { name: "Jack".into(), age: 32 })) |
| /// # } |
| /// # } |
| /// # |
| /// # fn main() { |
| /// # async { |
| /// // A service returning Result<Record, _> |
| /// let service = DatabaseService::new("127.0.0.1:8080"); |
| /// |
| /// // Map the response into a new response |
| /// let mut new_service = service.map_response(|record| record.name); |
| /// |
| /// // Call the new service |
| /// let id = 13; |
| /// let name = new_service |
| /// .ready() |
| /// .await? |
| /// .call(id) |
| /// .await?; |
| /// # Ok::<(), u8>(()) |
| /// # }; |
| /// # } |
| /// ``` |
| </span><span class="kw">fn </span>map_response<F, Response>(<span class="self">self</span>, f: F) -> MapResponse<<span class="self">Self</span>, F> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| F: FnOnce(<span class="self">Self</span>::Response) -> Response + Clone, |
| { |
| MapResponse::new(<span class="self">self</span>, f) |
| } |
| |
| <span class="doccomment">/// Maps this service's error value to a different value. This does not |
| /// alter the behaviour of the [`poll_ready`] method. |
| /// |
| /// This method can be used to change the [`Error`] type of the service |
| /// into a different type. It is similar to the [`Result::map_err`] method. |
| /// |
| /// [`Error`]: crate::Service::Error |
| /// [`poll_ready`]: crate::Service::poll_ready |
| /// |
| /// # Example |
| /// ``` |
| /// # use std::task::{Poll, Context}; |
| /// # use tower::{Service, ServiceExt}; |
| /// # |
| /// # struct DatabaseService; |
| /// # impl DatabaseService { |
| /// # fn new(address: &str) -> Self { |
| /// # DatabaseService |
| /// # } |
| /// # } |
| /// # |
| /// # struct Error { |
| /// # pub code: u32, |
| /// # pub message: String |
| /// # } |
| /// # |
| /// # impl Service<u32> for DatabaseService { |
| /// # type Response = String; |
| /// # type Error = Error; |
| /// # type Future = futures_util::future::Ready<Result<String, Error>>; |
| /// # |
| /// # fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// # Poll::Ready(Ok(())) |
| /// # } |
| /// # |
| /// # fn call(&mut self, request: u32) -> Self::Future { |
| /// # futures_util::future::ready(Ok(String::new())) |
| /// # } |
| /// # } |
| /// # |
| /// # fn main() { |
| /// # async { |
| /// // A service returning Result<_, Error> |
| /// let service = DatabaseService::new("127.0.0.1:8080"); |
| /// |
| /// // Map the error to a new error |
| /// let mut new_service = service.map_err(|err| err.code); |
| /// |
| /// // Call the new service |
| /// let id = 13; |
| /// let code = new_service |
| /// .ready() |
| /// .await? |
| /// .call(id) |
| /// .await |
| /// .unwrap_err(); |
| /// # Ok::<(), u32>(()) |
| /// # }; |
| /// # } |
| /// ``` |
| </span><span class="kw">fn </span>map_err<F, Error>(<span class="self">self</span>, f: F) -> MapErr<<span class="self">Self</span>, F> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| F: FnOnce(<span class="self">Self</span>::Error) -> Error + Clone, |
| { |
| MapErr::new(<span class="self">self</span>, f) |
| } |
| |
| <span class="doccomment">/// Maps this service's result type (`Result<Self::Response, Self::Error>`) |
| /// to a different value, regardless of whether the future succeeds or |
| /// fails. |
| /// |
| /// This is similar to the [`map_response`] and [`map_err`] combinators, |
| /// except that the *same* function is invoked when the service's future |
| /// completes, whether it completes successfully or fails. This function |
| /// takes the [`Result`] returned by the service's future, and returns a |
| /// [`Result`]. |
| /// |
| /// Like the standard library's [`Result::and_then`], this method can be |
| /// used to implement control flow based on `Result` values. For example, it |
| /// may be used to implement error recovery, by turning some [`Err`] |
| /// responses from the service into [`Ok`] responses. Similarly, some |
| /// successful responses from the service could be rejected, by returning an |
| /// [`Err`] conditionally, depending on the value inside the [`Ok`.] Finally, |
| /// this method can also be used to implement behaviors that must run when a |
| /// service's future completes, regardless of whether it succeeded or failed. |
| /// |
| /// This method can be used to change the [`Response`] type of the service |
| /// into a different type. It can also be used to change the [`Error`] type |
| /// of the service. However, because the [`map_result`] function is not applied |
| /// to the errors returned by the service's [`poll_ready`] method, it must |
| /// be possible to convert the service's [`Error`] type into the error type |
| /// returned by the [`map_result`] function. This is trivial when the function |
| /// returns the same error type as the service, but in other cases, it can |
| /// be useful to use [`BoxError`] to erase differing error types. |
| /// |
| /// # Examples |
| /// |
| /// Recovering from certain errors: |
| /// |
| /// ``` |
| /// # use std::task::{Poll, Context}; |
| /// # use tower::{Service, ServiceExt}; |
| /// # |
| /// # struct DatabaseService; |
| /// # impl DatabaseService { |
| /// # fn new(address: &str) -> Self { |
| /// # DatabaseService |
| /// # } |
| /// # } |
| /// # |
| /// # struct Record { |
| /// # pub name: String, |
| /// # pub age: u16 |
| /// # } |
| /// # #[derive(Debug)] |
| /// # enum DbError { |
| /// # Parse(std::num::ParseIntError), |
| /// # NoRecordsFound, |
| /// # } |
| /// # |
| /// # impl Service<u32> for DatabaseService { |
| /// # type Response = Vec<Record>; |
| /// # type Error = DbError; |
| /// # type Future = futures_util::future::Ready<Result<Vec<Record>, DbError>>; |
| /// # |
| /// # fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// # Poll::Ready(Ok(())) |
| /// # } |
| /// # |
| /// # fn call(&mut self, request: u32) -> Self::Future { |
| /// # futures_util::future::ready(Ok(vec![Record { name: "Jack".into(), age: 32 }])) |
| /// # } |
| /// # } |
| /// # |
| /// # fn main() { |
| /// # async { |
| /// // A service returning Result<Vec<Record>, DbError> |
| /// let service = DatabaseService::new("127.0.0.1:8080"); |
| /// |
| /// // If the database returns no records for the query, we just want an empty `Vec`. |
| /// let mut new_service = service.map_result(|result| match result { |
| /// // If the error indicates that no records matched the query, return an empty |
| /// // `Vec` instead. |
| /// Err(DbError::NoRecordsFound) => Ok(Vec::new()), |
| /// // Propagate all other responses (`Ok` and `Err`) unchanged |
| /// x => x, |
| /// }); |
| /// |
| /// // Call the new service |
| /// let id = 13; |
| /// let name = new_service |
| /// .ready() |
| /// .await? |
| /// .call(id) |
| /// .await?; |
| /// # Ok::<(), DbError>(()) |
| /// # }; |
| /// # } |
| /// ``` |
| /// |
| /// Rejecting some `Ok` responses: |
| /// |
| /// ``` |
| /// # use std::task::{Poll, Context}; |
| /// # use tower::{Service, ServiceExt}; |
| /// # |
| /// # struct DatabaseService; |
| /// # impl DatabaseService { |
| /// # fn new(address: &str) -> Self { |
| /// # DatabaseService |
| /// # } |
| /// # } |
| /// # |
| /// # struct Record { |
| /// # pub name: String, |
| /// # pub age: u16 |
| /// # } |
| /// # type DbError = String; |
| /// # type AppError = String; |
| /// # |
| /// # impl Service<u32> for DatabaseService { |
| /// # type Response = Record; |
| /// # type Error = DbError; |
| /// # type Future = futures_util::future::Ready<Result<Record, DbError>>; |
| /// # |
| /// # fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// # Poll::Ready(Ok(())) |
| /// # } |
| /// # |
| /// # fn call(&mut self, request: u32) -> Self::Future { |
| /// # futures_util::future::ready(Ok(Record { name: "Jack".into(), age: 32 })) |
| /// # } |
| /// # } |
| /// # |
| /// # fn main() { |
| /// # async { |
| /// use tower::BoxError; |
| /// |
| /// // A service returning Result<Record, DbError> |
| /// let service = DatabaseService::new("127.0.0.1:8080"); |
| /// |
| /// // If the user is zero years old, return an error. |
| /// let mut new_service = service.map_result(|result| { |
| /// let record = result?; |
| /// |
| /// if record.age == 0 { |
| /// // Users must have been born to use our app! |
| /// let app_error = AppError::from("users cannot be 0 years old!"); |
| /// |
| /// // Box the error to erase its type (as it can be an `AppError` |
| /// // *or* the inner service's `DbError`). |
| /// return Err(BoxError::from(app_error)); |
| /// } |
| /// |
| /// // Otherwise, return the record. |
| /// Ok(record) |
| /// }); |
| /// |
| /// // Call the new service |
| /// let id = 13; |
| /// let record = new_service |
| /// .ready() |
| /// .await? |
| /// .call(id) |
| /// .await?; |
| /// # Ok::<(), BoxError>(()) |
| /// # }; |
| /// # } |
| /// ``` |
| /// |
| /// Performing an action that must be run for both successes and failures: |
| /// |
| /// ``` |
| /// # use std::convert::TryFrom; |
| /// # use std::task::{Poll, Context}; |
| /// # use tower::{Service, ServiceExt}; |
| /// # |
| /// # struct DatabaseService; |
| /// # impl DatabaseService { |
| /// # fn new(address: &str) -> Self { |
| /// # DatabaseService |
| /// # } |
| /// # } |
| /// # |
| /// # impl Service<u32> for DatabaseService { |
| /// # type Response = String; |
| /// # type Error = u8; |
| /// # type Future = futures_util::future::Ready<Result<String, u8>>; |
| /// # |
| /// # fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// # Poll::Ready(Ok(())) |
| /// # } |
| /// # |
| /// # fn call(&mut self, request: u32) -> Self::Future { |
| /// # futures_util::future::ready(Ok(String::new())) |
| /// # } |
| /// # } |
| /// # |
| /// # fn main() { |
| /// # async { |
| /// // A service returning Result<Record, DbError> |
| /// let service = DatabaseService::new("127.0.0.1:8080"); |
| /// |
| /// // Print a message whenever a query completes. |
| /// let mut new_service = service.map_result(|result| { |
| /// println!("query completed; success={}", result.is_ok()); |
| /// result |
| /// }); |
| /// |
| /// // Call the new service |
| /// let id = 13; |
| /// let response = new_service |
| /// .ready() |
| /// .await? |
| /// .call(id) |
| /// .await; |
| /// # response |
| /// # }; |
| /// # } |
| /// ``` |
| /// |
| /// [`map_response`]: ServiceExt::map_response |
| /// [`map_err`]: ServiceExt::map_err |
| /// [`map_result`]: ServiceExt::map_result |
| /// [`Error`]: crate::Service::Error |
| /// [`Response`]: crate::Service::Response |
| /// [`poll_ready`]: crate::Service::poll_ready |
| /// [`BoxError`]: crate::BoxError |
| </span><span class="kw">fn </span>map_result<F, Response, Error>(<span class="self">self</span>, f: F) -> MapResult<<span class="self">Self</span>, F> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| Error: From<<span class="self">Self</span>::Error>, |
| F: FnOnce(<span class="prelude-ty">Result</span><<span class="self">Self</span>::Response, <span class="self">Self</span>::Error>) -> <span class="prelude-ty">Result</span><Response, Error> + Clone, |
| { |
| MapResult::new(<span class="self">self</span>, f) |
| } |
| |
| <span class="doccomment">/// Composes a function *in front of* the service. |
| /// |
| /// This adapter produces a new service that passes each value through the |
| /// given function `f` before sending it to `self`. |
| /// |
| /// # Example |
| /// ``` |
| /// # use std::convert::TryFrom; |
| /// # use std::task::{Poll, Context}; |
| /// # use tower::{Service, ServiceExt}; |
| /// # |
| /// # struct DatabaseService; |
| /// # impl DatabaseService { |
| /// # fn new(address: &str) -> Self { |
| /// # DatabaseService |
| /// # } |
| /// # } |
| /// # |
| /// # impl Service<String> for DatabaseService { |
| /// # type Response = String; |
| /// # type Error = u8; |
| /// # type Future = futures_util::future::Ready<Result<String, u8>>; |
| /// # |
| /// # fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// # Poll::Ready(Ok(())) |
| /// # } |
| /// # |
| /// # fn call(&mut self, request: String) -> Self::Future { |
| /// # futures_util::future::ready(Ok(String::new())) |
| /// # } |
| /// # } |
| /// # |
| /// # fn main() { |
| /// # async { |
| /// // A service taking a String as a request |
| /// let service = DatabaseService::new("127.0.0.1:8080"); |
| /// |
| /// // Map the request to a new request |
| /// let mut new_service = service.map_request(|id: u32| id.to_string()); |
| /// |
| /// // Call the new service |
| /// let id = 13; |
| /// let response = new_service |
| /// .ready() |
| /// .await? |
| /// .call(id) |
| /// .await; |
| /// # response |
| /// # }; |
| /// # } |
| /// ``` |
| </span><span class="kw">fn </span>map_request<F, NewRequest>(<span class="self">self</span>, f: F) -> MapRequest<<span class="self">Self</span>, F> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| F: FnMut(NewRequest) -> Request, |
| { |
| MapRequest::new(<span class="self">self</span>, f) |
| } |
| |
| <span class="doccomment">/// Composes this service with a [`Filter`] that conditionally accepts or |
| /// rejects requests based on a [predicate]. |
| /// |
| /// This adapter produces a new service that passes each value through the |
| /// given function `predicate` before sending it to `self`. |
| /// |
| /// # Example |
| /// ``` |
| /// # use std::convert::TryFrom; |
| /// # use std::task::{Poll, Context}; |
| /// # use tower::{Service, ServiceExt}; |
| /// # |
| /// # struct DatabaseService; |
| /// # impl DatabaseService { |
| /// # fn new(address: &str) -> Self { |
| /// # DatabaseService |
| /// # } |
| /// # } |
| /// # |
| /// # #[derive(Debug)] enum DbError { |
| /// # Parse(std::num::ParseIntError) |
| /// # } |
| /// # |
| /// # impl std::fmt::Display for DbError { |
| /// # fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { std::fmt::Debug::fmt(self, f) } |
| /// # } |
| /// # impl std::error::Error for DbError {} |
| /// # impl Service<u32> for DatabaseService { |
| /// # type Response = String; |
| /// # type Error = DbError; |
| /// # type Future = futures_util::future::Ready<Result<String, DbError>>; |
| /// # |
| /// # fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// # Poll::Ready(Ok(())) |
| /// # } |
| /// # |
| /// # fn call(&mut self, request: u32) -> Self::Future { |
| /// # futures_util::future::ready(Ok(String::new())) |
| /// # } |
| /// # } |
| /// # |
| /// # fn main() { |
| /// # async { |
| /// // A service taking a u32 as a request and returning Result<_, DbError> |
| /// let service = DatabaseService::new("127.0.0.1:8080"); |
| /// |
| /// // Fallibly map the request to a new request |
| /// let mut new_service = service |
| /// .filter(|id_str: &str| id_str.parse().map_err(DbError::Parse)); |
| /// |
| /// // Call the new service |
| /// let id = "13"; |
| /// let response = new_service |
| /// .ready() |
| /// .await? |
| /// .call(id) |
| /// .await; |
| /// # response |
| /// # }; |
| /// # } |
| /// ``` |
| /// |
| /// [`Filter`]: crate::filter::Filter |
| /// [predicate]: crate::filter::Predicate |
| </span><span class="attribute">#[cfg(feature = <span class="string">"filter"</span>)] |
| #[cfg_attr(docsrs, doc(cfg(feature = <span class="string">"filter"</span>)))] |
| </span><span class="kw">fn </span>filter<F, NewRequest>(<span class="self">self</span>, filter: F) -> <span class="kw">crate</span>::filter::Filter<<span class="self">Self</span>, F> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| F: <span class="kw">crate</span>::filter::Predicate<NewRequest>, |
| { |
| <span class="kw">crate</span>::filter::Filter::new(<span class="self">self</span>, filter) |
| } |
| |
| <span class="doccomment">/// Composes this service with an [`AsyncFilter`] that conditionally accepts or |
| /// rejects requests based on an [async predicate]. |
| /// |
| /// This adapter produces a new service that passes each value through the |
| /// given function `predicate` before sending it to `self`. |
| /// |
| /// # Example |
| /// ``` |
| /// # use std::convert::TryFrom; |
| /// # use std::task::{Poll, Context}; |
| /// # use tower::{Service, ServiceExt}; |
| /// # |
| /// # #[derive(Clone)] struct DatabaseService; |
| /// # impl DatabaseService { |
| /// # fn new(address: &str) -> Self { |
| /// # DatabaseService |
| /// # } |
| /// # } |
| /// # #[derive(Debug)] |
| /// # enum DbError { |
| /// # Rejected |
| /// # } |
| /// # impl std::fmt::Display for DbError { |
| /// # fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { std::fmt::Debug::fmt(self, f) } |
| /// # } |
| /// # impl std::error::Error for DbError {} |
| /// # |
| /// # impl Service<u32> for DatabaseService { |
| /// # type Response = String; |
| /// # type Error = DbError; |
| /// # type Future = futures_util::future::Ready<Result<String, DbError>>; |
| /// # |
| /// # fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// # Poll::Ready(Ok(())) |
| /// # } |
| /// # |
| /// # fn call(&mut self, request: u32) -> Self::Future { |
| /// # futures_util::future::ready(Ok(String::new())) |
| /// # } |
| /// # } |
| /// # |
| /// # fn main() { |
| /// # async { |
| /// // A service taking a u32 as a request and returning Result<_, DbError> |
| /// let service = DatabaseService::new("127.0.0.1:8080"); |
| /// |
| /// /// Returns `true` if we should query the database for an ID. |
| /// async fn should_query(id: u32) -> bool { |
| /// // ... |
| /// # true |
| /// } |
| /// |
| /// // Filter requests based on `should_query`. |
| /// let mut new_service = service |
| /// .filter_async(|id: u32| async move { |
| /// if should_query(id).await { |
| /// return Ok(id); |
| /// } |
| /// |
| /// Err(DbError::Rejected) |
| /// }); |
| /// |
| /// // Call the new service |
| /// let id = 13; |
| /// # let id: u32 = id; |
| /// let response = new_service |
| /// .ready() |
| /// .await? |
| /// .call(id) |
| /// .await; |
| /// # response |
| /// # }; |
| /// # } |
| /// ``` |
| /// |
| /// [`AsyncFilter`]: crate::filter::AsyncFilter |
| /// [asynchronous predicate]: crate::filter::AsyncPredicate |
| </span><span class="attribute">#[cfg(feature = <span class="string">"filter"</span>)] |
| #[cfg_attr(docsrs, doc(cfg(feature = <span class="string">"filter"</span>)))] |
| </span><span class="kw">fn </span>filter_async<F, NewRequest>(<span class="self">self</span>, filter: F) -> <span class="kw">crate</span>::filter::AsyncFilter<<span class="self">Self</span>, F> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| F: <span class="kw">crate</span>::filter::AsyncPredicate<NewRequest>, |
| { |
| <span class="kw">crate</span>::filter::AsyncFilter::new(<span class="self">self</span>, filter) |
| } |
| |
| <span class="doccomment">/// Composes an asynchronous function *after* this service. |
| /// |
| /// This takes a function or closure returning a future, and returns a new |
| /// `Service` that chains that function after this service's [`Future`]. The |
| /// new `Service`'s future will consist of this service's future, followed |
| /// by the future returned by calling the chained function with the future's |
| /// [`Output`] type. The chained function is called regardless of whether |
| /// this service's future completes with a successful response or with an |
| /// error. |
| /// |
| /// This method can be thought of as an equivalent to the [`futures` |
| /// crate]'s [`FutureExt::then`] combinator, but acting on `Service`s that |
| /// _return_ futures, rather than on an individual future. Similarly to that |
| /// combinator, [`ServiceExt::then`] can be used to implement asynchronous |
| /// error recovery, by calling some asynchronous function with errors |
| /// returned by this service. Alternatively, it may also be used to call a |
| /// fallible async function with the successful response of this service. |
| /// |
| /// This method can be used to change the [`Response`] type of the service |
| /// into a different type. It can also be used to change the [`Error`] type |
| /// of the service. However, because the `then` function is not applied |
| /// to the errors returned by the service's [`poll_ready`] method, it must |
| /// be possible to convert the service's [`Error`] type into the error type |
| /// returned by the `then` future. This is trivial when the function |
| /// returns the same error type as the service, but in other cases, it can |
| /// be useful to use [`BoxError`] to erase differing error types. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # use std::task::{Poll, Context}; |
| /// # use tower::{Service, ServiceExt}; |
| /// # |
| /// # struct DatabaseService; |
| /// # impl DatabaseService { |
| /// # fn new(address: &str) -> Self { |
| /// # DatabaseService |
| /// # } |
| /// # } |
| /// # |
| /// # type Record = (); |
| /// # type DbError = (); |
| /// # |
| /// # impl Service<u32> for DatabaseService { |
| /// # type Response = Record; |
| /// # type Error = DbError; |
| /// # type Future = futures_util::future::Ready<Result<Record, DbError>>; |
| /// # |
| /// # fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// # Poll::Ready(Ok(())) |
| /// # } |
| /// # |
| /// # fn call(&mut self, request: u32) -> Self::Future { |
| /// # futures_util::future::ready(Ok(())) |
| /// # } |
| /// # } |
| /// # |
| /// # fn main() { |
| /// // A service returning Result<Record, DbError> |
| /// let service = DatabaseService::new("127.0.0.1:8080"); |
| /// |
| /// // An async function that attempts to recover from errors returned by the |
| /// // database. |
| /// async fn recover_from_error(error: DbError) -> Result<Record, DbError> { |
| /// // ... |
| /// # Ok(()) |
| /// } |
| /// # async { |
| /// |
| /// // If the database service returns an error, attempt to recover by |
| /// // calling `recover_from_error`. Otherwise, return the successful response. |
| /// let mut new_service = service.then(|result| async move { |
| /// match result { |
| /// Ok(record) => Ok(record), |
| /// Err(e) => recover_from_error(e).await, |
| /// } |
| /// }); |
| /// |
| /// // Call the new service |
| /// let id = 13; |
| /// let record = new_service |
| /// .ready() |
| /// .await? |
| /// .call(id) |
| /// .await?; |
| /// # Ok::<(), DbError>(()) |
| /// # }; |
| /// # } |
| /// ``` |
| /// |
| /// [`Future`]: crate::Service::Future |
| /// [`Output`]: std::future::Future::Output |
| /// [`futures` crate]: https://docs.rs/futures |
| /// [`FutureExt::then`]: https://docs.rs/futures/latest/futures/future/trait.FutureExt.html#method.then |
| /// [`Error`]: crate::Service::Error |
| /// [`Response`]: crate::Service::Response |
| /// [`poll_ready`]: crate::Service::poll_ready |
| /// [`BoxError`]: crate::BoxError |
| </span><span class="kw">fn </span>then<F, Response, Error, Fut>(<span class="self">self</span>, f: F) -> Then<<span class="self">Self</span>, F> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| Error: From<<span class="self">Self</span>::Error>, |
| F: FnOnce(<span class="prelude-ty">Result</span><<span class="self">Self</span>::Response, <span class="self">Self</span>::Error>) -> Fut + Clone, |
| Fut: Future<Output = <span class="prelude-ty">Result</span><Response, Error>>, |
| { |
| Then::new(<span class="self">self</span>, f) |
| } |
| |
| <span class="doccomment">/// Composes a function that transforms futures produced by the service. |
| /// |
| /// This takes a function or closure returning a future computed from the future returned by |
| /// the service's [`call`] method, as opposed to the responses produced by the future. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # use std::task::{Poll, Context}; |
| /// # use tower::{Service, ServiceExt, BoxError}; |
| /// # |
| /// # struct DatabaseService; |
| /// # impl DatabaseService { |
| /// # fn new(address: &str) -> Self { |
| /// # DatabaseService |
| /// # } |
| /// # } |
| /// # |
| /// # type Record = (); |
| /// # type DbError = crate::BoxError; |
| /// # |
| /// # impl Service<u32> for DatabaseService { |
| /// # type Response = Record; |
| /// # type Error = DbError; |
| /// # type Future = futures_util::future::Ready<Result<Record, DbError>>; |
| /// # |
| /// # fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { |
| /// # Poll::Ready(Ok(())) |
| /// # } |
| /// # |
| /// # fn call(&mut self, request: u32) -> Self::Future { |
| /// # futures_util::future::ready(Ok(())) |
| /// # } |
| /// # } |
| /// # |
| /// # fn main() { |
| /// use std::time::Duration; |
| /// use tokio::time::timeout; |
| /// |
| /// // A service returning Result<Record, DbError> |
| /// let service = DatabaseService::new("127.0.0.1:8080"); |
| /// # async { |
| /// |
| /// let mut new_service = service.map_future(|future| async move { |
| /// let res = timeout(Duration::from_secs(1), future).await?; |
| /// Ok::<_, BoxError>(res) |
| /// }); |
| /// |
| /// // Call the new service |
| /// let id = 13; |
| /// let record = new_service |
| /// .ready() |
| /// .await? |
| /// .call(id) |
| /// .await?; |
| /// # Ok::<(), BoxError>(()) |
| /// # }; |
| /// # } |
| /// ``` |
| /// |
| /// Note that normally you wouldn't implement timeouts like this and instead use [`Timeout`]. |
| /// |
| /// [`call`]: crate::Service::call |
| /// [`Timeout`]: crate::timeout::Timeout |
| </span><span class="kw">fn </span>map_future<F, Fut, Response, Error>(<span class="self">self</span>, f: F) -> MapFuture<<span class="self">Self</span>, F> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| F: FnMut(<span class="self">Self</span>::Future) -> Fut, |
| Error: From<<span class="self">Self</span>::Error>, |
| Fut: Future<Output = <span class="prelude-ty">Result</span><Response, Error>>, |
| { |
| MapFuture::new(<span class="self">self</span>, f) |
| } |
| |
| <span class="doccomment">/// Convert the service into a [`Service`] + [`Send`] trait object. |
| /// |
| /// See [`BoxService`] for more details. |
| /// |
| /// If `Self` implements the [`Clone`] trait, the [`boxed_clone`] method |
| /// can be used instead, to produce a boxed service which will also |
| /// implement [`Clone`]. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use tower::{Service, ServiceExt, BoxError, service_fn, util::BoxService}; |
| /// # |
| /// # struct Request; |
| /// # struct Response; |
| /// # impl Response { |
| /// # fn new() -> Self { Self } |
| /// # } |
| /// |
| /// let service = service_fn(|req: Request| async { |
| /// Ok::<_, BoxError>(Response::new()) |
| /// }); |
| /// |
| /// let service: BoxService<Request, Response, BoxError> = service |
| /// .map_request(|req| { |
| /// println!("received request"); |
| /// req |
| /// }) |
| /// .map_response(|res| { |
| /// println!("response produced"); |
| /// res |
| /// }) |
| /// .boxed(); |
| /// # let service = assert_service(service); |
| /// # fn assert_service<S, R>(svc: S) -> S |
| /// # where S: Service<R> { svc } |
| /// ``` |
| /// |
| /// [`Service`]: crate::Service |
| /// [`boxed_clone`]: Self::boxed_clone |
| </span><span class="kw">fn </span>boxed(<span class="self">self</span>) -> BoxService<Request, <span class="self">Self</span>::Response, <span class="self">Self</span>::Error> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized + Send + <span class="lifetime">'static</span>, |
| <span class="self">Self</span>::Future: Send + <span class="lifetime">'static</span>, |
| { |
| BoxService::new(<span class="self">self</span>) |
| } |
| |
| <span class="doccomment">/// Convert the service into a [`Service`] + [`Clone`] + [`Send`] trait object. |
| /// |
| /// This is similar to the [`boxed`] method, but it requires that `Self` implement |
| /// [`Clone`], and the returned boxed service implements [`Clone`]. |
| /// See [`BoxCloneService`] for more details. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use tower::{Service, ServiceExt, BoxError, service_fn, util::BoxCloneService}; |
| /// # |
| /// # struct Request; |
| /// # struct Response; |
| /// # impl Response { |
| /// # fn new() -> Self { Self } |
| /// # } |
| /// |
| /// let service = service_fn(|req: Request| async { |
| /// Ok::<_, BoxError>(Response::new()) |
| /// }); |
| /// |
| /// let service: BoxCloneService<Request, Response, BoxError> = service |
| /// .map_request(|req| { |
| /// println!("received request"); |
| /// req |
| /// }) |
| /// .map_response(|res| { |
| /// println!("response produced"); |
| /// res |
| /// }) |
| /// .boxed_clone(); |
| /// |
| /// // The boxed service can still be cloned. |
| /// service.clone(); |
| /// # let service = assert_service(service); |
| /// # fn assert_service<S, R>(svc: S) -> S |
| /// # where S: Service<R> { svc } |
| /// ``` |
| /// |
| /// [`Service`]: crate::Service |
| /// [`boxed`]: Self::boxed |
| </span><span class="kw">fn </span>boxed_clone(<span class="self">self</span>) -> BoxCloneService<Request, <span class="self">Self</span>::Response, <span class="self">Self</span>::Error> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Clone + Sized + Send + <span class="lifetime">'static</span>, |
| <span class="self">Self</span>::Future: Send + <span class="lifetime">'static</span>, |
| { |
| BoxCloneService::new(<span class="self">self</span>) |
| } |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized, Request> ServiceExt<Request> <span class="kw">for </span>T <span class="kw">where </span>T: tower_service::Service<Request> {} |
| |
| <span class="doccomment">/// Convert an `Option<Layer>` into a [`Layer`]. |
| /// |
| /// ``` |
| /// # use std::time::Duration; |
| /// # use tower::Service; |
| /// # use tower::builder::ServiceBuilder; |
| /// use tower::util::option_layer; |
| /// # use tower::timeout::TimeoutLayer; |
| /// # async fn wrap<S>(svc: S) where S: Service<(), Error = &'static str> + 'static + Send, S::Future: Send { |
| /// # let timeout = Some(Duration::new(10, 0)); |
| /// // Layer to apply a timeout if configured |
| /// let maybe_timeout = option_layer(timeout.map(TimeoutLayer::new)); |
| /// |
| /// ServiceBuilder::new() |
| /// .layer(maybe_timeout) |
| /// .service(svc); |
| /// # } |
| /// ``` |
| /// |
| /// [`Layer`]: crate::layer::Layer |
| </span><span class="kw">pub fn </span>option_layer<L>(layer: <span class="prelude-ty">Option</span><L>) -> Either<L, Identity> { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(layer) = layer { |
| Either::A(layer) |
| } <span class="kw">else </span>{ |
| Either::B(Identity::new()) |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="tower" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
