Function futures_util::future::try_select [−][src]
pub fn try_select<A, B>(future1: A, future2: B) -> TrySelect<A, B>ⓘ where
A: TryFuture + Unpin,
B: TryFuture + Unpin,
Waits for either one of two differently-typed futures to complete.
This function will return a new future which awaits for either one of both futures to complete. The returned future will finish with both the value resolved and a future representing the completion of the other work.
Note that this function consumes the receiving futures and returns a wrapped version of them.
Also note that if both this and the second future have the same
success/error type you can use the Either::factor_first
method to
conveniently extract out the value at the end.
Examples
use futures::future::{self, Either, Future, FutureExt, TryFuture, TryFutureExt}; // A poor-man's try_join implemented on top of select fn try_join<A, B, E>(a: A, b: B) -> impl TryFuture<Ok=(A::Ok, B::Ok), Error=E> where A: TryFuture<Error = E> + Unpin + 'static, B: TryFuture<Error = E> + Unpin + 'static, E: 'static, { future::try_select(a, b).then(|res| -> Box<dyn Future<Output = Result<_, _>> + Unpin> { match res { Ok(Either::Left((x, b))) => Box::new(b.map_ok(move |y| (x, y))), Ok(Either::Right((y, a))) => Box::new(a.map_ok(move |x| (x, y))), Err(Either::Left((e, _))) => Box::new(future::err(e)), Err(Either::Right((e, _))) => Box::new(future::err(e)), } }) }