blob: 2e5b6aa16edea3e6164537f698e93a82f8d2ca13 [file] [log] [blame]
use {Future, IntoFuture, Poll};
use super::chain::Chain;
/// Future for the `and_then` combinator, chaining a computation onto the end of
/// another future which completes successfully.
///
/// This is created by the `Future::and_then` method.
#[derive(Debug)]
#[must_use = "futures do nothing unless polled"]
pub struct AndThen<A, B, F> where A: Future, B: IntoFuture {
state: Chain<A, B::Future, F>,
}
pub fn new<A, B, F>(future: A, f: F) -> AndThen<A, B, F>
where A: Future,
B: IntoFuture,
{
AndThen {
state: Chain::new(future, f),
}
}
impl<A, B, F> Future for AndThen<A, B, F>
where A: Future,
B: IntoFuture<Error=A::Error>,
F: FnOnce(A::Item) -> B,
{
type Item = B::Item;
type Error = B::Error;
fn poll(&mut self) -> Poll<B::Item, B::Error> {
self.state.poll(|result, f| {
result.map(|e| {
Err(f(e).into_future())
})
})
}
}