Struct tower::util::FutureService

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pub struct FutureService<F, S> { /* private fields */ }
Expand description

A type that implements Service for a Future that produces a Service.

See future_service for more details.

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impl<F, S> FutureService<F, S>

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pub fn new(future: F) -> Self

Returns a new FutureService for the given future.

A FutureService allows you to treat a future that resolves to a service as a service. This can be useful for services that are created asynchronously.

Example
use tower::{service_fn, Service, ServiceExt};
use tower::util::FutureService;
use std::convert::Infallible;

// A future which outputs a type implementing `Service`.
let future_of_a_service = async {
    let svc = service_fn(|_req: ()| async { Ok::<_, Infallible>("ok") });
    Ok::<_, Infallible>(svc)
};

// Wrap the future with a `FutureService`, allowing it to be used
// as a service without awaiting the future's completion:
let mut svc = FutureService::new(Box::pin(future_of_a_service));

// Now, when we wait for the service to become ready, it will
// drive the future to completion internally.
let svc = svc.ready().await.unwrap();
let res = svc.call(()).await.unwrap();
Regarding the Unpin bound

The Unpin bound on F is necessary because the future will be polled in Service::poll_ready which doesn’t have a pinned receiver (it takes &mut self and not self: Pin<&mut Self>). So we cannot put the future into a Pin without requiring Unpin.

This will most likely come up if you’re calling future_service with an async block. In that case you can use Box::pin(async { ... }) as shown in the example.

Trait Implementations§

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impl<F: Clone, S: Clone> Clone for FutureService<F, S>

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fn clone(&self) -> FutureService<F, S>

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<F, S> Debug for FutureService<F, S>where S: Debug,

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<F, S, R, E> Service<R> for FutureService<F, S>where F: Future<Output = Result<S, E>> + Unpin, S: Service<R, Error = E>,

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type Response = <S as Service<R>>::Response

Responses given by the service.
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type Error = E

Errors produced by the service.
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type Future = <S as Service<R>>::Future

The future response value.
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fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>>

Returns Poll::Ready(Ok(())) when the service is able to process requests. Read more
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fn call(&mut self, req: R) -> Self::Future

Process the request and return the response asynchronously. Read more

Auto Trait Implementations§

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impl<F, S> RefUnwindSafe for FutureService<F, S>where F: RefUnwindSafe, S: RefUnwindSafe,

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impl<F, S> Send for FutureService<F, S>where F: Send, S: Send,

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impl<F, S> Sync for FutureService<F, S>where F: Sync, S: Sync,

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impl<F, S> Unpin for FutureService<F, S>where F: Unpin, S: Unpin,

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impl<F, S> UnwindSafe for FutureService<F, S>where F: UnwindSafe, S: UnwindSafe,

Blanket Implementations§

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impl<T> Any for Twhere T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for Twhere T: ?Sized,

const: unstable · source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for Twhere T: ?Sized,

const: unstable · source§

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for Twhere U: From<T>,

const: unstable · source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T, Request> ServiceExt<Request> for Twhere T: Service<Request> + ?Sized,

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fn ready(&mut self) -> Ready<'_, Self, Request> where Self: Sized,

Yields a mutable reference to the service when it is ready to accept a request.
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fn ready_and(&mut self) -> ReadyAnd<'_, Self, Request>where Self: Sized,

👎Deprecated since 0.4.6: please use the ServiceExt::ready method instead
Yields a mutable reference to the service when it is ready to accept a request.
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fn ready_oneshot(self) -> ReadyOneshot<Self, Request> where Self: Sized,

Yields the service when it is ready to accept a request.
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fn oneshot(self, req: Request) -> Oneshot<Self, Request> where Self: Sized,

Consume this Service, calling with the providing request once it is ready.
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fn call_all<S>(self, reqs: S) -> CallAll<Self, S>where Self: Sized, Self::Error: Into<BoxError>, S: Stream<Item = Request>,

Process all requests from the given Stream, and produce a Stream of their responses. Read more
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fn and_then<F>(self, f: F) -> AndThen<Self, F>where Self: Sized, F: Clone,

Executes a new future after this service’s future resolves. This does not alter the behaviour of the poll_ready method. Read more
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fn map_response<F, Response>(self, f: F) -> MapResponse<Self, F>where Self: Sized, F: FnOnce(Self::Response) -> Response + Clone,

Maps this service’s response value to a different value. This does not alter the behaviour of the poll_ready method. Read more
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fn map_err<F, Error>(self, f: F) -> MapErr<Self, F>where Self: Sized, F: FnOnce(Self::Error) -> Error + Clone,

Maps this service’s error value to a different value. This does not alter the behaviour of the poll_ready method. Read more
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fn map_result<F, Response, Error>(self, f: F) -> MapResult<Self, F>where Self: Sized, Error: From<Self::Error>, F: FnOnce(Result<Self::Response, Self::Error>) -> Result<Response, Error> + Clone,

Maps this service’s result type (Result<Self::Response, Self::Error>) to a different value, regardless of whether the future succeeds or fails. Read more
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fn map_request<F, NewRequest>(self, f: F) -> MapRequest<Self, F>where Self: Sized, F: FnMut(NewRequest) -> Request,

Composes a function in front of the service. Read more
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fn then<F, Response, Error, Fut>(self, f: F) -> Then<Self, F>where Self: Sized, Error: From<Self::Error>, F: FnOnce(Result<Self::Response, Self::Error>) -> Fut + Clone, Fut: Future<Output = Result<Response, Error>>,

Composes an asynchronous function after this service. Read more
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fn map_future<F, Fut, Response, Error>(self, f: F) -> MapFuture<Self, F>where Self: Sized, F: FnMut(Self::Future) -> Fut, Error: From<Self::Error>, Fut: Future<Output = Result<Response, Error>>,

Composes a function that transforms futures produced by the service. Read more
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fn boxed(self) -> BoxService<Request, Self::Response, Self::Error>where Self: Sized + Send + 'static, Self::Future: Send + 'static,

Convert the service into a Service + Send trait object. Read more
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fn boxed_clone(self) -> BoxCloneService<Request, Self::Response, Self::Error>where Self: Clone + Sized + Send + 'static, Self::Future: Send + 'static,

Convert the service into a Service + Clone + Send trait object. Read more
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impl<T> ToOwned for Twhere T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
const: unstable · source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
const: unstable · source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.