Function tokio::prelude::stream::poll_fn

pub fn poll_fn<T, E, F>(f: F) -> PollFn<F> where
    F: FnMut() -> Result<Async<Option<T>>, E>, 

Creates a new stream wrapping around a function returning Poll.

Polling the returned stream delegates to the wrapped function.

Examples

use futures::stream::poll_fn;
use futures::{Async, Poll};

let mut counter = 1usize;

let read_stream = poll_fn(move || -> Poll<Option<String>, std::io::Error> {
    if counter == 0 { return Ok(Async::Ready(None)); }
    counter -= 1;
    Ok(Async::Ready(Some("Hello, World!".to_owned())))
});