Polls multiple futures simultaneously, resolving to a Result containing either a tuple of the successful outputs or an error.

try_join! is similar to [join!], but completes immediately if any of the futures return an error.

This macro is only usable inside of async functions, closures, and blocks. It is also gated behind the async-await feature of this library, which is activated by default.

Examples

When used on multiple futures that return Ok, try_join! will return Ok of a tuple of the values:

# futures::executor::block_on(async {
use futures::try_join;

let a = async { Ok::<i32, i32>(1) };
let b = async { Ok::<i32, i32>(2) };
assert_eq!(try_join!(a, b), Ok((1, 2)));

// `try_join!` is variadic, so you can pass any number of futures
let c = async { Ok::<i32, i32>(3) };
let d = async { Ok::<i32, i32>(4) };
let e = async { Ok::<i32, i32>(5) };
assert_eq!(try_join!(c, d, e), Ok((3, 4, 5)));
# });

If one of the futures resolves to an error, try_join! will return that error:

# futures::executor::block_on(async {
use futures::try_join;

let a = async { Ok::<i32, i32>(1) };
let b = async { Err::<u64, i32>(2) };

assert_eq!(try_join!(a, b), Err(2));
# });