tower/util/
service_fn.rs

1use std::fmt;
2use std::future::Future;
3use std::task::{Context, Poll};
4use tower_service::Service;
5
6/// Returns a new [`ServiceFn`] with the given closure.
7///
8/// This lets you build a [`Service`] from an async function that returns a [`Result`].
9///
10/// # Example
11///
12/// ```
13/// use tower::{service_fn, Service, ServiceExt, BoxError};
14/// # struct Request;
15/// # impl Request {
16/// #     fn new() -> Self { Self }
17/// # }
18/// # struct Response(&'static str);
19/// # impl Response {
20/// #     fn new(body: &'static str) -> Self {
21/// #         Self(body)
22/// #     }
23/// #     fn into_body(self) -> &'static str { self.0 }
24/// # }
25///
26/// # #[tokio::main]
27/// # async fn main() -> Result<(), BoxError> {
28/// async fn handle(request: Request) -> Result<Response, BoxError> {
29///     let response = Response::new("Hello, World!");
30///     Ok(response)
31/// }
32///
33/// let mut service = service_fn(handle);
34///
35/// let response = service
36///     .ready()
37///     .await?
38///     .call(Request::new())
39///     .await?;
40///
41/// assert_eq!("Hello, World!", response.into_body());
42/// #
43/// # Ok(())
44/// # }
45/// ```
46pub fn service_fn<T>(f: T) -> ServiceFn<T> {
47    ServiceFn { f }
48}
49
50/// A [`Service`] implemented by a closure.
51///
52/// See [`service_fn`] for more details.
53#[derive(Copy, Clone)]
54pub struct ServiceFn<T> {
55    f: T,
56}
57
58impl<T> fmt::Debug for ServiceFn<T> {
59    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
60        f.debug_struct("ServiceFn")
61            .field("f", &format_args!("{}", std::any::type_name::<T>()))
62            .finish()
63    }
64}
65
66impl<T, F, Request, R, E> Service<Request> for ServiceFn<T>
67where
68    T: FnMut(Request) -> F,
69    F: Future<Output = Result<R, E>>,
70{
71    type Response = R;
72    type Error = E;
73    type Future = F;
74
75    fn poll_ready(&mut self, _: &mut Context<'_>) -> Poll<Result<(), E>> {
76        Ok(()).into()
77    }
78
79    fn call(&mut self, req: Request) -> Self::Future {
80        (self.f)(req)
81    }
82}
tower/util/service_fn.rs

tower/util/
service_fn.rs
