# Function futures_util::future::try_select [−] [src]

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    pub fn try_select<A, B>(future1: A, future2: B) -> TrySelect<A, B>ⓘNotable traits for TrySelect<A, B>impl<A: Unpin, B: Unpin> Future for TrySelect<A, B> where
        A: TryFuture,
        B: TryFuture,     type Output = Result<Either<(A::Ok, B), (B::Ok, A)>, Either<(A::Error, B), (B::Error, A)>>; 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)),
            }
        })
    }