Function futures_util::future::lazy

Important traits for Lazy<F>

impl<R, F> Future for Lazy<F> where
    F: FnOnce(&mut Context) -> R,  type Output = R;

pub fn lazy<F, R>(f: F) -> Lazy<F> where
    F: FnOnce(&mut Context) -> R, 

Creates a new future that allows delayed execution of a closure.

The provided closure is only run once the future is polled.

Examples

#![feature(async_await, await_macro, futures_api)]
use futures::future;

let a = future::lazy(|_| 1);
assert_eq!(await!(a), 1);

let b = future::lazy(|_| -> i32 {
    panic!("oh no!")
});
drop(b); // closure is never run