Struct futures::stream::Once

#[must_use = "streams do nothing unless polled"]pub struct Once<T, E>(_);

A stream which emits single element and then EOF.

This stream will never block and is always ready.

Trait Implementations

impl<T: Debug, E: Debug> Debug for Once<T, E>

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

Formats the value using the given formatter.

impl<T, E> Stream for Once<T, E>

type Item = T

The type of item this stream will yield on success.

type Error = E

The type of error this stream may generate.

fn poll(&mut self) -> Poll<Option<T>, E>

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 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 as IntoIterator>::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 as IntoIterator>::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 as Stream>::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, 

👎 Deprecated:

functionality provided by select now

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.

fn inspect<F>(self, f: F) -> Inspect<Self, F> where
    F: FnMut(&Self::Item),
    Self: Sized, 

Do something with each item of this stream, afterwards passing it on.

fn inspect_err<F>(self, f: F) -> InspectErr<Self, F> where
    F: FnMut(&Self::Error),
    Self: Sized, 

Do something with the error of this stream, afterwards passing it on.