Trait FutureExt

pub trait FutureExt: Future {
    // Provided methods
    fn poll(&mut self, cx: &mut Context<'_>) -> Poll<Self::Output>
       where Self: Unpin { ... }
    fn or<F>(self, other: F) -> Or<Self, F> 
       where Self: Sized,
             F: Future<Output = Self::Output> { ... }
    fn race<F>(self, other: F) -> Race<Self, F> 
       where Self: Sized,
             F: Future<Output = Self::Output> { ... }
    fn catch_unwind(self) -> CatchUnwind<Self> 
       where Self: Sized + UnwindSafe { ... }
    fn boxed<'a>(
        self,
    ) -> Pin<Box<dyn Future<Output = Self::Output> + Send + 'a>>
       where Self: Sized + Send + 'a { ... }
    fn boxed_local<'a>(self) -> Pin<Box<dyn Future<Output = Self::Output> + 'a>>
       where Self: Sized + 'a { ... }
}

Extension trait for Future.

Provided Methods

fn poll(&mut self, cx: &mut Context<'_>) -> Poll<Self::Output>

where Self: Unpin,

A convenience for calling Future::poll() on !Unpin types.

fn or<F>(self, other: F) -> Or<Self, F>

where Self: Sized, F: Future<Output = Self::Output>,

Returns the result of self or other future, preferring self if both are ready.

If you need to treat the two futures fairly without a preference for either, use the race() function or the FutureExt::race() method.

Examples

use futures_lite::future::{pending, ready, FutureExt};

assert_eq!(ready(1).or(pending()).await, 1);
assert_eq!(pending().or(ready(2)).await, 2);

// The first future wins.
assert_eq!(ready(1).or(ready(2)).await, 1);

fn race<F>(self, other: F) -> Race<Self, F>

where Self: Sized, F: Future<Output = Self::Output>,

Returns the result of self or other future, with no preference if both are ready.

Each time Race is polled, the two inner futures are polled in random order. Therefore, no future takes precedence over the other if both can complete at the same time.

If you have preference for one of the futures, use the or() function or the FutureExt::or() method.

Examples

use futures_lite::future::{pending, ready, FutureExt};

assert_eq!(ready(1).race(pending()).await, 1);
assert_eq!(pending().race(ready(2)).await, 2);

// One of the two futures is randomly chosen as the winner.
let res = ready(1).race(ready(2)).await;

fn catch_unwind(self) -> CatchUnwind<Self>

where Self: Sized + UnwindSafe,

Catches panics while polling the future.

Examples

use futures_lite::future::FutureExt;

let fut1 = async {}.catch_unwind();
let fut2 = async { panic!() }.catch_unwind();

assert!(fut1.await.is_ok());
assert!(fut2.await.is_err());

fn boxed<'a>(self) -> Pin<Box<dyn Future<Output = Self::Output> + Send + 'a>>

where Self: Sized + Send + 'a,

Boxes the future and changes its type to dyn Future + Send + 'a.

Examples

use futures_lite::future::{self, FutureExt};

let a = future::ready('a');
let b = future::pending();

// Futures of different types can be stored in
// the same collection when they are boxed:
let futures = vec![a.boxed(), b.boxed()];

fn boxed_local<'a>(self) -> Pin<Box<dyn Future<Output = Self::Output> + 'a>>

where Self: Sized + 'a,

Boxes the future and changes its type to dyn Future + 'a.

Examples

use futures_lite::future::{self, FutureExt};

let a = future::ready('a');
let b = future::pending();

// Futures of different types can be stored in
// the same collection when they are boxed:
let futures = vec![a.boxed_local(), b.boxed_local()];

Implementors

impl<F: Future + ?Sized> FutureExt for F