Struct futures::future::Fuse

#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct Fuse<Fut> where
    Fut: Future,  { /* fields omitted */ }

Future for the fuse method.

Methods

impl<Fut> Fuse<Fut> where
    Fut: Future, 

Important traits for Fuse<Fut>

impl<Fut> Future for Fuse<Fut> where
    Fut: Future,  type Output = <Fut as Future>::Output;

pub fn terminated() -> Fuse<Fut>

Creates a new Fuse-wrapped future which is already terminated.

This can be useful in combination with looping and the select! macro, which bypasses terminated futures.

Examples

#![feature(async_await)]
use futures::channel::mpsc;
use futures::future::{Fuse, FusedFuture, FutureExt};
use futures::select;
use futures::stream::StreamExt;
use futures::pin_mut;

let (sender, mut stream) = mpsc::unbounded();

// Send a few messages into the stream
sender.unbounded_send(()).unwrap();
sender.unbounded_send(()).unwrap();
drop(sender);

// Use `Fuse::termianted()` to create an already-terminated future
// which may be instantiated later.
let foo_printer = Fuse::terminated();
pin_mut!(foo_printer);

loop {
    select! {
        _ = foo_printer => {},
        () = stream.select_next_some() => {
            if !foo_printer.is_terminated() {
                println!("Foo is already being printed!");
            } else {
                foo_printer.set(async {
                    // do some other async operations
                    println!("Printing foo from `foo_printer` future");
                }.fuse());
            }
        },
        complete => break, // `foo_printer` is terminated and the stream is done
    }
}

Trait Implementations

impl<Fut> Future for Fuse<Fut> where
    Fut: Future, 

type Output = <Fut as Future>::Output

The type of value produced on completion.

fn poll(
    self: Pin<&mut Fuse<Fut>>,
    cx: &mut Context
) -> Poll<<Fut as Future>::Output>

Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available.

impl<Fut> Debug for Fuse<Fut> where
    Fut: Debug + Future, 

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

Formats the value using the given formatter.

impl<Fut> FusedFuture for Fuse<Fut> where
    Fut: Future, 

fn is_terminated(&self) -> bool

Returns true if the underlying future should no longer be polled.