Trait AsyncGenerator

pub trait AsyncGenerator {
    type Yield;
    type Return;

    // Required method
    fn poll_resume(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<GeneratorState<Self::Yield, Self::Return>>;
}

Generators, also commonly referred to as coroutines.

Required Associated Types

type Yield

The type of value this generator yields.

This associated type corresponds to the yield expression and the values which are allowed to be returned each time a generator yields. For example an iterator-as-a-generator would likely have this type as T, the type being iterated over.

type Return

The type of value this generator returns.

This corresponds to the type returned from a generator either with a return statement or implicitly as the last expression of a generator literal. For example futures would use this as Result<T, E> as it represents a completed future.

Required Methods

fn poll_resume( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<GeneratorState<Self::Yield, Self::Return>>

Resumes the execution of this generator.

This function will resume execution of the generator or start execution if it hasn’t already. This call will return back into the generator’s last suspension point, resuming execution from the latest yield. The generator will continue executing until it either yields or returns, at which point this function will return.

Return value

The GeneratorState enum returned from this function indicates what state the generator is in upon returning. If the Yielded variant is returned then the generator has reached a suspension point and a value has been yielded out. Generators in this state are available for resumption at a later point.

If Complete is returned then the generator has completely finished with the value provided. It is invalid for the generator to be resumed again.

Panics

This function may panic if it is called after the Complete variant has been returned previously. While generator literals in the language are guaranteed to panic on resuming after Complete, this is not guaranteed for all implementations of the Generator trait.

Implementors

impl<Fut, Y, R> AsyncGenerator for AsyncGen<Fut, Y>

where Fut: Future<Output = Return<R>>,

type Yield = Y

type Return = R