Struct futures_util::future::Fuse

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

Future for the fuse method.

Methods

impl<Fut: Future> Fuse<Fut>

Important traits for Fuse<Fut>

impl<Fut: Future> Future for Fuse<Fut> type Output = Fut::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

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: Debug + Future> Debug for Fuse<Fut>

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

Formats the value using the given formatter.

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

type Output = Fut::Output

The type of value produced on completion.

fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Fut::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: Future> FusedFuture for Fuse<Fut>

fn is_terminated(&self) -> bool

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