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extern crate futures;
use self::futures::{Async, Future};
pub trait TapFutureOps<T, E> {
fn tap_ready<R, F: FnOnce(&T) -> R>(self, f: F) -> Self;
fn tap_not_ready<R, F: FnOnce() -> R>(self, f: F) -> Self;
fn tap_err<R, F: FnOnce(&E) -> R>(self, f: F) -> Self;
}
impl<T, E, FUT: Future<Item = T, Error = E>> TapFutureOps<T, E> for FUT {
fn tap_ready<R, F: FnOnce(&T) -> R>(mut self, f: F) -> Self {
if let Ok(Async::Ready(ref val)) = self.poll() {
let _ = f(val);
}
self
}
fn tap_not_ready<R, F: FnOnce() -> R>(mut self, f: F) -> Self {
if let Ok(Async::NotReady) = self.poll() {
let _ = f();
}
self
}
fn tap_err<R, F: FnOnce(&E) -> R>(mut self, f: F) -> Self {
if let Err(ref val) = self.poll() {
let _ = f(val);
}
self
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn ready() {
let mut foo = 0;
let future = futures::future::result::<i32, i32>(Ok(5));
let _ = future.tap_ready(|x| foo += *x);
assert_eq!(foo, 5);
}
#[test]
fn not_ready() {
let mut foo = 0;
let future = futures::future::empty::<i32, i32>();
match future.tap_not_ready(|| foo += 5).poll() {
Ok(Async::NotReady) => assert_eq!(foo, 5),
_ => unreachable!()
}
}
#[test]
fn error() {
let mut foo = 0;
let future = futures::future::result::<i32, i32>(Err(5));
let _ = future.tap_err(|x| foo += *x);
assert_eq!(foo, 5);
}
}