Struct Promise

pub struct Promise<T: 'static = ()>(/* private fields */);

Represents an ongoing operation which produces a result.

Implementations

impl<T: Send + Sync + 'static> Promise<T>

pub fn new() -> (Self, impl FnOnce(T) + Send)

Creates a new lightweight promise and an associated resolve function.

Example

let (promise, resolve) = Promise::<i32>::new();
Task::spawn(|| {
    Task::delay(Duration::from_secs(1));
    resolve(10);
})
.unwrap();
println!(
    "n = {}",
    select! {
        n = promise.done() => n,
    }
);

pub fn done(&self) -> impl Selectable<&T> + '_

A Selectable event which occurs when the promise is resolved.

pub fn spawn(f: impl FnOnce() -> T + Send + 'static) -> Self

Spawns a task to run the given function and returns a Promise that resolves with the result when it returns. Panics on failure; see Promise::try_spawn().

pub fn try_spawn(f: impl FnOnce() -> T + Send + 'static) -> Result<Self, Error>

Spawns a task to run the given function and returns a Promise that resolves with the result when it returns.

pub fn then<U: Send + Sync + 'static>( &self, f: impl FnOnce(&T) -> U + Send + 'static, ) -> Promise<U>

Spawns a new promise which, upon the completion of self, runs f.

pub fn then_or<U: Send + Sync + 'static>( &self, ctx: Context, default: U, f: impl FnOnce(&T) -> U + Send + 'static, ) -> Promise<U>

Spawns a new promise which, upon the completion of self, runs f. If ctx is cancelled before self completes, the result is default.

pub fn then_some<U: Send + Sync + 'static>( &self, ctx: Context, f: impl FnOnce(&T) -> U + Send + 'static, ) -> Promise<Option<U>>

Spawns a new promise which, upon the completion of self, runs f. If ctx is cancelled before self completes, the result is None.

Trait Implementations

impl<T: 'static> Clone for Promise<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

const fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.