Macro futures_util::select

macro_rules! select {
    () => { ... };
    ($(
        $name:ident => $body:expr,
    )*) => { ... };
}

Polls multiple futures simultaneously, executing the branch for the future that finishes first.

select! can select over futures with different output types, but each branch has to have the same return type. Inside each branch, the respective future's output is available via a variable with the same name as the future.

This macro is only usable inside of async functions, closures, and blocks.

Examples

#![feature(pin, async_await, await_macro, futures_api)]
use futures::{select, future};
let mut a = future::ready(4);
let mut b: future::Empty<()> = future::empty();

let res = select! {
    a => a + 1,
    b => 0,
};
assert_eq!(res, 5);