Struct Promise 

pub struct Promise<T>(/* private fields */);

A box for resolving a Future.

A Promise is a write-once box which corresponds with a Future and may be used to resolve it.

A Promise is initially pending, and is completed once it is consumed, either by its set method, or by going out of scope. The former is “fulfilling” the Promise; the latter is leaving it “unfulfilled”.

It may only be created in a pair with a Future using the function future_promise().

Implementations

impl<T> Promise<T>

pub fn set(self, v: T)

Fulfill the Promise by resolving the corresponding Future with a value.

pub fn canceled(&self) -> bool

Return true if the corresponding Future no longer exists, and so any value set would be discarded.

let (fut, prom) = future_promise();

thread::spawn(move || {
    let mut s = State::new();
    while !prom.canceled() {
        match s.perform_action() {
            None => (),
            Some(res) => { prom.set(res); break },
        }
    }
});
// ...
mem::drop(fut);

Trait Implementations

impl<T: Debug> Debug for Promise<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.