Struct futures::stream::FuturesUnordered

#[must_use = "streams do nothing unless polled"]
pub struct FuturesUnordered<F> { /* fields omitted */ }

An unbounded queue of futures.

This "combinator" also serves a special function in this library, providing the ability to maintain a queue of futures that and manage driving them all to completion.

Futures are pushed into this queue and their realized values are yielded as they are ready. This structure is optimized to manage a large number of futures. Futures managed by FuturesUnordered will only be polled when they generate notifications. This reduces the required amount of work needed to coordinate large numbers of futures.

When a FuturesUnordered is first created, it does not contain any futures. Calling poll in this state will result in Ok(Async::Ready(None)) to be returned. Futures are submitted to the queue using push; however, the future will not be polled at this point. FuturesUnordered will only poll managged futures when FuturesUnordered::poll is called. As such, it is important to call poll after pushing new futures.

If FuturesUnordered::poll returns Ok(Async::Ready(None)) this means that the queue is currently not managing any futures. A future may be submitted to the queue at a later time. At that point, a call to FuturesUnordered::poll will either return the future's resolved value or Ok(Async::NotReady) if the future has not yet completed.

Note that you can create a ready-made FuturesUnordered via the futures_unordered function in the stream module, or you can start with a blank queue with the FuturesUnordered::new constructor.

Methods

impl<T> FuturesUnordered<T> where
    T: Future, 

fn new() -> FuturesUnordered<T>

Constructs a new, empty FuturesUnordered

The returned FuturesUnordered does not contain any futures and, in this state, FuturesUnordered::poll will return Ok(Async::Ready(None)).

impl<T> FuturesUnordered<T>

fn len(&self) -> usize

Returns the number of futures contained by the queue.

This represents the total number of in-flight futures.

fn is_empty(&self) -> bool

Returns true if the queue contains no futures

fn push(&mut self, future: T)

Push a future into the queue.

This function submits the given future to the queue for managing. This function will not call poll on the submitted future. The caller must ensure that FuturesUnordered::poll is called in order to receive task notifications.

Trait Implementations

impl<T: Send> Send for FuturesUnordered<T>

impl<T: Sync> Sync for FuturesUnordered<T>

impl<T> Stream for FuturesUnordered<T> where
    T: Future, 

type Item = T::Item

The type of item this stream will yield on success.

type Error = T::Error

The type of error this stream may generate.

fn poll(&mut self) -> Poll<Option<T::Item>, T::Error>

Attempt to pull out the next value of this stream, returning None if the stream is finished.

fn wait(self) -> Wait<Self> where
    Self: Sized, 

Creates an iterator which blocks the current thread until each item of this stream is resolved.

fn boxed(self) -> BoxStream<Self::Item, Self::Error> where
    Self: Sized + Send + 'static, 

Convenience function for turning this stream into a trait object.

fn into_future(self) -> StreamFuture<Self> where
    Self: Sized, 

Converts this stream into a Future.

fn map<U, F>(self, f: F) -> Map<Self, F> where
    F: FnMut(Self::Item) -> U,
    Self: Sized, 

Converts a stream of type T to a stream of type U.

fn map_err<U, F>(self, f: F) -> MapErr<Self, F> where
    F: FnMut(Self::Error) -> U,
    Self: Sized, 

Converts a stream of error type T to a stream of error type U.

fn filter<F>(self, f: F) -> Filter<Self, F> where
    F: FnMut(&Self::Item) -> bool,
    Self: Sized, 

Filters the values produced by this stream according to the provided predicate.

fn filter_map<F, B>(self, f: F) -> FilterMap<Self, F> where
    F: FnMut(Self::Item) -> Option<B>,
    Self: Sized, 

Filters the values produced by this stream while simultaneously mapping them to a different type.

fn then<F, U>(self, f: F) -> Then<Self, F, U> where
    F: FnMut(Result<Self::Item, Self::Error>) -> U,
    U: IntoFuture,
    Self: Sized, 

Chain on a computation for when a value is ready, passing the resulting item to the provided closure f.

fn and_then<F, U>(self, f: F) -> AndThen<Self, F, U> where
    F: FnMut(Self::Item) -> U,
    U: IntoFuture<Error = Self::Error>,
    Self: Sized, 

Chain on a computation for when a value is ready, passing the successful results to the provided closure f.

fn or_else<F, U>(self, f: F) -> OrElse<Self, F, U> where
    F: FnMut(Self::Error) -> U,
    U: IntoFuture<Item = Self::Item>,
    Self: Sized, 

Chain on a computation for when an error happens, passing the erroneous result to the provided closure f.

fn collect(self) -> Collect<Self> where
    Self: Sized, 

Collect all of the values of this stream into a vector, returning a future representing the result of that computation.

fn concat2(self) -> Concat2<Self> where
    Self: Sized,
    Self::Item: Extend<Self::Item::Item> + IntoIterator + Default, 

Concatenate all results of a stream into a single extendable destination, returning a future representing the end result.

fn concat(self) -> Concat<Self> where
    Self: Sized,
    Self::Item: Extend<Self::Item::Item> + IntoIterator, 

Deprecated since 0.1.14

: please use Stream::concat2 instead

Concatenate all results of a stream into a single extendable destination, returning a future representing the end result.

fn fold<F, T, Fut>(self, init: T, f: F) -> Fold<Self, F, Fut, T> where
    F: FnMut(T, Self::Item) -> Fut,
    Fut: IntoFuture<Item = T>,
    Self::Error: From<Fut::Error>,
    Self: Sized, 

Execute an accumulating computation over a stream, collecting all the values into one final result.

fn flatten(self) -> Flatten<Self> where
    Self::Item: Stream,
    Self::Item::Error: From<Self::Error>,
    Self: Sized, 

Flattens a stream of streams into just one continuous stream.

fn skip_while<P, R>(self, pred: P) -> SkipWhile<Self, P, R> where
    P: FnMut(&Self::Item) -> R,
    R: IntoFuture<Item = bool, Error = Self::Error>,
    Self: Sized, 

Skip elements on this stream while the predicate provided resolves to true.

fn take_while<P, R>(self, pred: P) -> TakeWhile<Self, P, R> where
    P: FnMut(&Self::Item) -> R,
    R: IntoFuture<Item = bool, Error = Self::Error>,
    Self: Sized, 

Take elements from this stream while the predicate provided resolves to true.

fn for_each<F, U>(self, f: F) -> ForEach<Self, F, U> where
    F: FnMut(Self::Item) -> U,
    U: IntoFuture<Item = (), Error = Self::Error>,
    Self: Sized, 

Runs this stream to completion, executing the provided closure for each element on the stream.

fn from_err<E: From<Self::Error>>(self) -> FromErr<Self, E> where
    Self: Sized, 

Map this stream's error to any error implementing From for this stream's Error, returning a new stream.

fn take(self, amt: u64) -> Take<Self> where
    Self: Sized, 

Creates a new stream of at most amt items of the underlying stream.

fn skip(self, amt: u64) -> Skip<Self> where
    Self: Sized, 

Creates a new stream which skips amt items of the underlying stream.

fn fuse(self) -> Fuse<Self> where
    Self: Sized, 

Fuse a stream such that poll will never again be called once it has finished.

fn by_ref(&mut self) -> &mut Self where
    Self: Sized, 

Borrows a stream, rather than consuming it.

fn catch_unwind(self) -> CatchUnwind<Self> where
    Self: Sized + UnwindSafe, 

Catches unwinding panics while polling the stream.

fn buffered(self, amt: usize) -> Buffered<Self> where
    Self::Item: IntoFuture<Error = Self::Error>,
    Self: Sized, 

An adaptor for creating a buffered list of pending futures.

fn buffer_unordered(self, amt: usize) -> BufferUnordered<Self> where
    Self::Item: IntoFuture<Error = Self::Error>,
    Self: Sized, 

An adaptor for creating a buffered list of pending futures (unordered).

fn merge<S>(self, other: S) -> Merge<Self, S> where
    S: Stream<Error = Self::Error>,
    Self: Sized, 

An adapter for merging the output of two streams.

fn zip<S>(self, other: S) -> Zip<Self, S> where
    S: Stream<Error = Self::Error>,
    Self: Sized, 

An adapter for zipping two streams together.

fn chain<S>(self, other: S) -> Chain<Self, S> where
    S: Stream<Item = Self::Item, Error = Self::Error>,
    Self: Sized, 

Adapter for chaining two stream.

fn peekable(self) -> Peekable<Self> where
    Self: Sized, 

Creates a new stream which exposes a peek method.

fn chunks(self, capacity: usize) -> Chunks<Self> where
    Self: Sized, 

An adaptor for chunking up items of the stream inside a vector.

fn select<S>(self, other: S) -> Select<Self, S> where
    S: Stream<Item = Self::Item, Error = Self::Error>,
    Self: Sized, 

Creates a stream that selects the next element from either this stream or the provided one, whichever is ready first.

fn forward<S>(self, sink: S) -> Forward<Self, S> where
    S: Sink<SinkItem = Self::Item>,
    Self::Error: From<S::SinkError>,
    Self: Sized, 

A future that completes after the given stream has been fully processed into the sink, including flushing.

fn split(self) -> (SplitSink<Self>, SplitStream<Self>) where
    Self: Sink + Sized, 

Splits this Stream + Sink object into separate Stream and Sink objects.

impl<T: Debug> Debug for FuturesUnordered<T>

fn fmt(&self, fmt: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<T> Drop for FuturesUnordered<T>

fn drop(&mut self)

A method called when the value goes out of scope.