pub fn poll_immediate<F>(f: F) -> PollImmediate<F>ⓘNotable traits for PollImmediate<F>impl<T, F> Future for PollImmediate<F> where
F: Future<Output = T>, type Output = Option<T>; where
F: Future, Expand description
Creates a future that is immediately ready with an Option of a value. Specifically this means that poll always returns Poll::Ready.
Caution
When consuming the future by this function, note the following:
- This function does not guarantee that the future will run to completion, so it is generally incompatible with passing the non-cancellation-safe future by value.
- Even if the future is cancellation-safe, creating and dropping new futures frequently may lead to performance problems.
Examples
use futures::future;
let r = future::poll_immediate(async { 1_u32 });
assert_eq!(r.await, Some(1));
let p = future::poll_immediate(future::pending::<i32>());
assert_eq!(p.await, None);Reusing a future
use futures::{future, pin_mut};
let f = async {futures::pending!(); 42_u8};
pin_mut!(f);
assert_eq!(None, future::poll_immediate(&mut f).await);
assert_eq!(42, f.await);