Function futures_util::stream::iter_result

pub fn iter_result<J, T, E>(i: J) -> IterResult<J::IntoIter> where
    J: IntoIterator<Item = Result<T, E>>, 

Converts an Iterator over Results into a Stream which is always ready to yield the next value.

Iterators in Rust don't express the ability to block, so this adapter simply always calls iter.next() and returns that.

use futures::prelude::*;
use futures::stream;
use futures_executor::block_on;

let mut stream = stream::iter_result(vec![Ok(17), Err(false), Ok(19)]);
let (item, stream) = block_on(stream.next()).unwrap();
assert_eq!(Some(17), item);
let (err, stream) = block_on(stream.next()).unwrap_err();
assert_eq!(false, err);
let (item, stream) = block_on(stream.next()).unwrap();
assert_eq!(Some(19), item);
let (item, _) = block_on(stream.next()).unwrap();
assert_eq!(None, item);