Trait futures_util::stream::StreamExt
[−]
[src]
pub trait StreamExt: Stream { fn next(self) -> StreamFuture<Self>
where
Self: Sized, { ... } fn map<U, F>(self, f: F) -> Map<Self, F>
where
F: FnMut(Self::Item) -> U,
Self: Sized, { ... } fn map_err<U, F>(self, f: F) -> MapErr<Self, F>
where
F: FnMut(Self::Error) -> U,
Self: Sized, { ... } fn filter<R, P>(self, pred: P) -> Filter<Self, R, P>
where
P: FnMut(&Self::Item) -> R,
R: IntoFuture<Item = bool, Error = Self::Error>,
Self: Sized, { ... } fn filter_map<R, B, F>(self, f: F) -> FilterMap<Self, R, F>
where
F: FnMut(Self::Item) -> R,
R: IntoFuture<Item = Option<B>, Error = Self::Error>,
Self: Sized, { ... } fn then<U, F>(self, f: F) -> Then<Self, U, F>
where
F: FnMut(Result<Self::Item, Self::Error>) -> U,
U: IntoFuture,
Self: Sized, { ... } fn and_then<U, F>(self, f: F) -> AndThen<Self, U, F>
where
F: FnMut(Self::Item) -> U,
U: IntoFuture<Error = Self::Error>,
Self: Sized, { ... } fn or_else<U, F>(self, f: F) -> OrElse<Self, U, F>
where
F: FnMut(Self::Error) -> U,
U: IntoFuture<Item = Self::Item>,
Self: Sized, { ... } fn collect<C: Default + Extend<Self::Item>>(self) -> Collect<Self, C>
where
Self: Sized, { ... } fn concat(self) -> Concat<Self>
where
Self: Sized,
Self::Item: Extend<<Self::Item as IntoIterator>::Item> + IntoIterator + Default, { ... } fn fold<T, Fut, F>(self, init: T, f: F) -> Fold<Self, Fut, T, F>
where
F: FnMut(T, Self::Item) -> Fut,
Fut: IntoFuture<Item = T, Error = Self::Error>,
Self: Sized, { ... } fn flatten(self) -> Flatten<Self>
where
Self::Item: Stream<Error = Self::Error>,
Self: Sized, { ... } fn skip_while<R, P>(self, pred: P) -> SkipWhile<Self, R, P>
where
P: FnMut(&Self::Item) -> R,
R: IntoFuture<Item = bool, Error = Self::Error>,
Self: Sized, { ... } fn take_while<R, P>(self, pred: P) -> TakeWhile<Self, R, P>
where
P: FnMut(&Self::Item) -> R,
R: IntoFuture<Item = bool, Error = Self::Error>,
Self: Sized, { ... } fn for_each<U, F>(self, f: F) -> ForEach<Self, U, F>
where
F: FnMut(Self::Item) -> U,
U: IntoFuture<Item = (), Error = Self::Error>,
Self: Sized, { ... } fn for_each_concurrent<U, F>(self, f: F) -> ForEachConcurrent<Self, U, F>
where
F: FnMut(Self::Item) -> U,
U: IntoFuture<Item = (), Error = Self::Error>,
Self: Sized, { ... } fn err_into<E>(self) -> ErrInto<Self, E>
where
Self: Sized,
Self::Error: Into<E>, { ... } fn take(self, amt: u64) -> Take<Self>
where
Self: Sized, { ... } fn skip(self, amt: u64) -> Skip<Self>
where
Self: Sized, { ... } fn fuse(self) -> Fuse<Self>
where
Self: Sized, { ... } fn by_ref(&mut self) -> &mut Self
where
Self: Sized, { ... } fn catch_unwind(self) -> CatchUnwind<Self>
where
Self: Sized + UnwindSafe, { ... } fn buffered(self, amt: usize) -> Buffered<Self>
where
Self::Item: IntoFuture<Error = Self::Error>,
Self: Sized, { ... } fn buffer_unordered(self, amt: usize) -> BufferUnordered<Self>
where
Self::Item: IntoFuture<Error = Self::Error>,
Self: Sized, { ... } fn zip<S>(self, other: S) -> Zip<Self, S>
where
S: Stream<Error = Self::Error>,
Self: Sized, { ... } fn chain<S>(self, other: S) -> Chain<Self, S>
where
S: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized, { ... } fn peekable(self) -> Peekable<Self>
where
Self: Sized, { ... } fn chunks(self, capacity: usize) -> Chunks<Self>
where
Self: Sized, { ... } fn select<S>(self, other: S) -> Select<Self, S>
where
S: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized, { ... } fn forward<S>(self, sink: S) -> Forward<Self, S>
where
S: Sink<SinkItem = Self::Item>,
Self::Error: From<S::SinkError>,
Self: Sized, { ... } fn split(self) -> (SplitSink<Self>, SplitStream<Self>)
where
Self: Sink + Sized, { ... } fn inspect<F>(self, f: F) -> Inspect<Self, F>
where
F: FnMut(&Self::Item),
Self: Sized, { ... } fn inspect_err<F>(self, f: F) -> InspectErr<Self, F>
where
F: FnMut(&Self::Error),
Self: Sized, { ... } fn recover<E, F>(self, f: F) -> Recover<Self, E, F>
where
F: FnMut(Self::Error) -> Option<Self::Item>,
Self: Sized, { ... } fn left<B>(self) -> Either<Self, B>
where
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized, { ... } fn right<B>(self) -> Either<B, Self>
where
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized, { ... } fn left_stream<B>(self) -> Either<Self, B>
where
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized, { ... } fn right_stream<B>(self) -> Either<B, Self>
where
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized, { ... } }
An extension trait for Stream
s that provides a variety of convenient
combinator functions.
Provided Methods
fn next(self) -> StreamFuture<Self> where
Self: Sized,
Self: Sized,
Converts this stream into a Future
.
A stream can be viewed as a future which will resolve to a pair containing
the next element of the stream plus the remaining stream. If the stream
terminates, then the next element is None
and the remaining stream is
still passed back, to allow reclamation of its resources.
The returned future can be used to compose streams and futures together by placing everything into the "world of futures".
fn map<U, F>(self, f: F) -> Map<Self, F> where
F: FnMut(Self::Item) -> U,
Self: Sized,
F: FnMut(Self::Item) -> U,
Self: Sized,
Converts a stream of type T
to a stream of type U
.
The provided closure is executed over all elements of this stream as
they are made available, and the callback will be executed inline with
calls to poll
.
Note that this function consumes the receiving stream and returns a
wrapped version of it, similar to the existing map
methods in the
standard library.
Examples
use futures::prelude::*; use futures_channel::mpsc; let (_tx, rx) = mpsc::channel::<i32>(1); let rx = rx.map(|x| x + 3);
fn map_err<U, F>(self, f: F) -> MapErr<Self, F> where
F: FnMut(Self::Error) -> U,
Self: Sized,
F: FnMut(Self::Error) -> U,
Self: Sized,
Converts a stream of error type T
to a stream of error type U
.
The provided closure is executed over all errors of this stream as
they are made available, and the callback will be executed inline with
calls to poll
.
Note that this function consumes the receiving stream and returns a
wrapped version of it, similar to the existing map_err
methods in the
standard library.
Examples
use futures::prelude::*; use futures_channel::mpsc; let (_tx, rx) = mpsc::channel::<i32>(1); let rx = rx.map_err(|_| 3);
fn filter<R, P>(self, pred: P) -> Filter<Self, R, P> where
P: FnMut(&Self::Item) -> R,
R: IntoFuture<Item = bool, Error = Self::Error>,
Self: Sized,
P: FnMut(&Self::Item) -> R,
R: IntoFuture<Item = bool, Error = Self::Error>,
Self: Sized,
Filters the values produced by this stream according to the provided predicate.
As values of this stream are made available, the provided predicate will
be run against them. If the predicate returns a Future
which resolves
to true
, then the stream will yield the value, but if the predicate
returns a Future
which resolves to false
, then the value will be
discarded and the next value will be produced.
All errors are passed through without filtering in this combinator.
Note that this function consumes the receiving stream and returns a
wrapped version of it, similar to the existing filter
methods in the
standard library.
Examples
use futures::prelude::*; use futures_channel::mpsc; let (_tx, rx) = mpsc::channel::<i32>(1); let evens = rx.filter(|x| Ok(x % 2 == 0));
fn filter_map<R, B, F>(self, f: F) -> FilterMap<Self, R, F> where
F: FnMut(Self::Item) -> R,
R: IntoFuture<Item = Option<B>, Error = Self::Error>,
Self: Sized,
F: FnMut(Self::Item) -> R,
R: IntoFuture<Item = Option<B>, Error = Self::Error>,
Self: Sized,
Filters the values produced by this stream while simultaneously mapping them to a different type.
As values of this stream are made available, the provided function will
be run on them. If the predicate returns Some(e)
then the stream will
yield the value e
, but if the predicate returns None
then the next
value will be produced.
All errors are passed through without filtering in this combinator.
Note that this function consumes the receiving stream and returns a
wrapped version of it, similar to the existing filter_map
methods in the
standard library.
Examples
use futures::prelude::*; use futures_channel::mpsc; let (_tx, rx) = mpsc::channel::<i32>(1); let evens_plus_one = rx.filter_map(|x| { Ok( if x % 0 == 2 { Some(x + 1) } else { None } ) });
fn then<U, F>(self, f: F) -> Then<Self, U, F> where
F: FnMut(Result<Self::Item, Self::Error>) -> U,
U: IntoFuture,
Self: Sized,
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
.
This function can be used to ensure a computation runs regardless of
the next value on the stream. The closure provided will be yielded a
Result
once a value is ready, and the returned future will then be run
to completion to produce the next value on this stream.
The returned value of the closure must implement the IntoFuture
trait
and can represent some more work to be done before the composed stream
is finished. Note that the Result
type implements the IntoFuture
trait so it is possible to simply alter the Result
yielded to the
closure and return it.
Note that this function consumes the receiving stream and returns a wrapped version of it.
Examples
use futures::prelude::*; use futures_channel::mpsc; let (_tx, rx) = mpsc::channel::<i32>(1); let rx = rx.then(|result| { match result { Ok(e) => Ok(e + 3), Err(_) => Err(4), } });
fn and_then<U, F>(self, f: F) -> AndThen<Self, U, F> where
F: FnMut(Self::Item) -> U,
U: IntoFuture<Error = Self::Error>,
Self: Sized,
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
.
This function can be used to run a unit of work when the next successful value on a stream is ready. The closure provided will be yielded a value when ready, and the returned future will then be run to completion to produce the next value on this stream.
Any errors produced by this stream will not be passed to the closure, and will be passed through.
The returned value of the closure must implement the IntoFuture
trait
and can represent some more work to be done before the composed stream
is finished. Note that the Result
type implements the IntoFuture
trait so it is possible to simply alter the Result
yielded to the
closure and return it.
Note that this function consumes the receiving stream and returns a wrapped version of it.
To process the entire stream and return a single future representing
success or error, use for_each
instead.
Examples
use futures::prelude::*; use futures_channel::mpsc; let (_tx, rx) = mpsc::channel::<i32>(1); let rx = rx.and_then(|result| { if result % 2 == 0 { Ok(Some(result)) } else { Ok(None) } });
fn or_else<U, F>(self, f: F) -> OrElse<Self, U, F> where
F: FnMut(Self::Error) -> U,
U: IntoFuture<Item = Self::Item>,
Self: Sized,
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
.
This function can be used to run a unit of work and attempt to recover from an error if one happens. The closure provided will be yielded an error when one appears, and the returned future will then be run to completion to produce the next value on this stream.
Any successful values produced by this stream will not be passed to the closure, and will be passed through.
The returned value of the closure must implement the IntoFuture
trait
and can represent some more work to be done before the composed stream
is finished. Note that the Result
type implements the IntoFuture
trait so it is possible to simply alter the Result
yielded to the
closure and return it.
Note that this function consumes the receiving stream and returns a wrapped version of it.
fn collect<C: Default + Extend<Self::Item>>(self) -> Collect<Self, C> where
Self: Sized,
Self: Sized,
Collect all of the values of this stream into a vector, returning a future representing the result of that computation.
This combinator will collect all successful results of this stream and
collect them into a Vec<Self::Item>
. If an error happens then all
collected elements will be dropped and the error will be returned.
The returned future will be resolved whenever an error happens or when
the stream returns Ok(None)
.
This method is only available when the std
feature of this
library is activated, and it is activated by default.
Examples
use std::thread; use futures::prelude::*; use futures_channel::mpsc; use futures_executor::block_on; let (mut tx, rx) = mpsc::unbounded(); thread::spawn(move || { for i in (0..5).rev() { tx.unbounded_send(i + 1).unwrap(); } }); let result = block_on(rx.collect()); assert_eq!(result, Ok(vec![5, 4, 3, 2, 1]));
fn concat(self) -> Concat<Self> where
Self: Sized,
Self::Item: Extend<<Self::Item as IntoIterator>::Item> + IntoIterator + Default,
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.
This combinator will extend the first item with the contents of all the successful results of the stream. If the stream is empty, the default value will be returned. If an error occurs, all the results will be dropped and the error will be returned.
Examples
use std::thread; use futures::prelude::*; use futures_channel::mpsc; use futures_executor::block_on; let (mut tx, rx) = mpsc::unbounded(); thread::spawn(move || { for i in (0..3).rev() { let n = i * 3; tx.unbounded_send(vec![n + 1, n + 2, n + 3]).unwrap(); } }); let result = block_on(rx.concat()); assert_eq!(result, Ok(vec![7, 8, 9, 4, 5, 6, 1, 2, 3]));
fn fold<T, Fut, F>(self, init: T, f: F) -> Fold<Self, Fut, T, F> where
F: FnMut(T, Self::Item) -> Fut,
Fut: IntoFuture<Item = T, Error = Self::Error>,
Self: Sized,
F: FnMut(T, Self::Item) -> Fut,
Fut: IntoFuture<Item = T, Error = Self::Error>,
Self: Sized,
Execute an accumulating computation over a stream, collecting all the values into one final result.
This combinator will collect all successful results of this stream according to the closure provided. The initial state is also provided to this method and then is returned again by each execution of the closure. Once the entire stream has been exhausted the returned future will resolve to this value.
If an error happens then collected state will be dropped and the error will be returned.
Examples
use futures::prelude::*; use futures::stream; use futures::future; use futures_executor::block_on; let number_stream = stream::iter_ok::<_, ()>(0..6); let sum = number_stream.fold(0, |acc, x| future::ok(acc + x)); assert_eq!(block_on(sum), Ok(15));
fn flatten(self) -> Flatten<Self> where
Self::Item: Stream<Error = Self::Error>,
Self: Sized,
Self::Item: Stream<Error = Self::Error>,
Self: Sized,
Flattens a stream of streams into just one continuous stream.
If this stream's elements are themselves streams then this combinator will flatten out the entire stream to one long chain of elements. Any errors are passed through without looking at them, but otherwise each individual stream will get exhausted before moving on to the next.
use std::thread; use futures::prelude::*; use futures_channel::mpsc; use futures_executor::block_on; let (tx1, rx1) = mpsc::unbounded::<i32>(); let (tx2, rx2) = mpsc::unbounded::<i32>(); let (tx3, rx3) = mpsc::unbounded(); thread::spawn(move || { tx1.unbounded_send(1).unwrap(); tx1.unbounded_send(2).unwrap(); }); thread::spawn(move || { tx2.unbounded_send(3).unwrap(); tx2.unbounded_send(4).unwrap(); }); thread::spawn(move || { tx3.unbounded_send(rx1).unwrap(); tx3.unbounded_send(rx2).unwrap(); }); let result = block_on(rx3.flatten().collect()); assert_eq!(result, Ok(vec![1, 2, 3, 4]));
fn skip_while<R, P>(self, pred: P) -> SkipWhile<Self, R, P> where
P: FnMut(&Self::Item) -> R,
R: IntoFuture<Item = bool, Error = Self::Error>,
Self: Sized,
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
.
This function, like Iterator::skip_while
, will skip elements on the
stream until the predicate
resolves to false
. Once one element
returns false all future elements will be returned from the underlying
stream.
fn take_while<R, P>(self, pred: P) -> TakeWhile<Self, R, P> where
P: FnMut(&Self::Item) -> R,
R: IntoFuture<Item = bool, Error = Self::Error>,
Self: Sized,
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
.
This function, like Iterator::take_while
, will take elements from the
stream until the predicate
resolves to false
. Once one element
returns false it will always return that the stream is done.
fn for_each<U, F>(self, f: F) -> ForEach<Self, U, F> where
F: FnMut(Self::Item) -> U,
U: IntoFuture<Item = (), Error = Self::Error>,
Self: Sized,
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.
The closure provided will be called for each item this stream resolves to successfully, producing a future. That future will then be executed to completion before moving on to the next item.
The returned value is a Future
where the Item
type is the completed
stream, and errors are otherwise threaded through. Any error on the
stream or in the provided future will cause iteration to be halted
immediately and the future will resolve to that error.
To process each item in the stream and produce another stream instead
of a single future, use and_then
instead.
fn for_each_concurrent<U, F>(self, f: F) -> ForEachConcurrent<Self, U, F> where
F: FnMut(Self::Item) -> U,
U: IntoFuture<Item = (), Error = Self::Error>,
Self: Sized,
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. This is similar to for_each
but may begin
processing an element while previous elements are still being processed.
When this stream successfully resolves to an item, the closure will be called to produce a future. That future will then be added to the set of futures to resolve.
The returned value is a Future
where the Item
type is the completed
stream, and errors are otherwise threaded through. Any error on the
stream or in the provided future will cause iteration to be halted
immediately and the future will resolve to that error.
To process each item in the stream and produce another stream instead
of a single future, use and_then
instead.
fn err_into<E>(self) -> ErrInto<Self, E> where
Self: Sized,
Self::Error: Into<E>,
Self: Sized,
Self::Error: Into<E>,
Map this stream's error to a different type using the Into
trait.
This function does for streams what try!
does for Result
,
by letting the compiler infer the type of the resulting error.
Just as map_err
above, this is useful for example to ensure
that streams have the same error type when used with
combinators.
Note that this function consumes the receiving stream and returns a wrapped version of it.
fn take(self, amt: u64) -> Take<Self> where
Self: Sized,
Self: Sized,
Creates a new stream of at most amt
items of the underlying stream.
Once amt
items have been yielded from this stream then it will always
return that the stream is done.
Errors
Any errors yielded from underlying stream, before the desired amount of items is reached, are passed through and do not affect the total number of items taken.
fn skip(self, amt: u64) -> Skip<Self> where
Self: Sized,
Self: Sized,
Creates a new stream which skips amt
items of the underlying stream.
Once amt
items have been skipped from this stream then it will always
return the remaining items on this stream.
Errors
All errors yielded from underlying stream are passed through and do not affect the total number of items skipped.
fn fuse(self) -> Fuse<Self> where
Self: Sized,
Self: Sized,
Fuse a stream such that poll
will never again be called once it has
finished.
Currently once a stream has returned None
from poll
any further
calls could exhibit bad behavior such as block forever, panic, never
return, etc. If it is known that poll
may be called after stream has
already finished, then this method can be used to ensure that it has
defined semantics.
Once a stream has been fuse
d and it finishes, then it will forever
return None
from poll
. This, unlike for the traits poll
method,
is guaranteed.
Also note that as soon as this stream returns None
it will be dropped
to reclaim resources associated with it.
fn by_ref(&mut self) -> &mut Self where
Self: Sized,
Self: Sized,
Borrows a stream, rather than consuming it.
This is useful to allow applying stream adaptors while still retaining ownership of the original stream.
use futures::prelude::*; use futures::stream; use futures::future; use futures_executor::block_on; let mut stream = stream::iter_ok::<_, ()>(1..5); let sum = block_on(stream.by_ref().take(2).fold(0, |a, b| future::ok(a + b))); assert_eq!(sum, Ok(3)); // You can use the stream again let sum = block_on(stream.take(2).fold(0, |a, b| future::ok(a + b))); assert_eq!(sum, Ok(7));
fn catch_unwind(self) -> CatchUnwind<Self> where
Self: Sized + UnwindSafe,
Self: Sized + UnwindSafe,
Catches unwinding panics while polling the stream.
Caught panic (if any) will be the last element of the resulting stream.
In general, panics within a stream can propagate all the way out to the task level. This combinator makes it possible to halt unwinding within the stream itself. It's most commonly used within task executors. This method should not be used for error handling.
Note that this method requires the UnwindSafe
bound from the standard
library. This isn't always applied automatically, and the standard
library provides an AssertUnwindSafe
wrapper type to apply it
after-the fact. To assist using this method, the Stream
trait is also
implemented for AssertUnwindSafe<S>
where S
implements Stream
.
This method is only available when the std
feature of this
library is activated, and it is activated by default.
Examples
use futures::prelude::*; use futures::stream; use futures_executor::block_on; let stream = stream::iter_ok::<_, bool>(vec![Some(10), None, Some(11)]); // panic on second element let stream_panicking = stream.map(|o| o.unwrap()); // collect all the results let stream = stream_panicking.catch_unwind().then(|r| Ok::<_, ()>(r)); let results: Vec<_> = block_on(stream.collect()).unwrap(); match results[0] { Ok(Ok(10)) => {} _ => panic!("unexpected result!"), } assert!(results[1].is_err()); assert_eq!(results.len(), 2);
fn buffered(self, amt: usize) -> Buffered<Self> where
Self::Item: IntoFuture<Error = Self::Error>,
Self: Sized,
Self::Item: IntoFuture<Error = Self::Error>,
Self: Sized,
An adaptor for creating a buffered list of pending futures.
If this stream's item can be converted into a future, then this adaptor
will buffer up to at most amt
futures and then return results in the
same order as the underlying stream. No more than amt
futures will be
buffered at any point in time, and less than amt
may also be buffered
depending on the state of each future.
The returned stream will be a stream of each future's result, with errors passed through whenever they occur.
This method is only available when the std
feature of this
library is activated, and it is activated by default.
fn buffer_unordered(self, amt: usize) -> BufferUnordered<Self> where
Self::Item: IntoFuture<Error = Self::Error>,
Self: Sized,
Self::Item: IntoFuture<Error = Self::Error>,
Self: Sized,
An adaptor for creating a buffered list of pending futures (unordered).
If this stream's item can be converted into a future, then this adaptor
will buffer up to amt
futures and then return results in the order
in which they complete. No more than amt
futures will be buffered at
any point in time, and less than amt
may also be buffered depending on
the state of each future.
The returned stream will be a stream of each future's result, with errors passed through whenever they occur.
This method is only available when the std
feature of this
library is activated, and it is activated by default.
fn zip<S>(self, other: S) -> Zip<Self, S> where
S: Stream<Error = Self::Error>,
Self: Sized,
S: Stream<Error = Self::Error>,
Self: Sized,
An adapter for zipping two streams together.
The zipped stream waits for both streams to produce an item, and then returns that pair. If an error happens, then that error will be returned immediately. If either stream ends then the zipped stream will also end.
fn chain<S>(self, other: S) -> Chain<Self, S> where
S: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized,
S: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized,
Adapter for chaining two stream.
The resulting stream emits elements from the first stream, and when first stream reaches the end, emits the elements from the second stream.
use futures::prelude::*; use futures::stream; use futures_executor::block_on; let stream1 = stream::iter_result(vec![Ok(10), Err(false)]); let stream2 = stream::iter_result(vec![Err(true), Ok(20)]); let stream = stream1.chain(stream2) .then(|result| Ok::<_, ()>(result)); let result: Vec<_> = block_on(stream.collect()).unwrap(); assert_eq!(result, vec![ Ok(10), Err(false), Err(true), Ok(20), ]);
fn peekable(self) -> Peekable<Self> where
Self: Sized,
Self: Sized,
Creates a new stream which exposes a peek
method.
Calling peek
returns a reference to the next item in the stream.
fn chunks(self, capacity: usize) -> Chunks<Self> where
Self: Sized,
Self: Sized,
An adaptor for chunking up items of the stream inside a vector.
This combinator will attempt to pull items from this stream and buffer
them into a local vector. At most capacity
items will get buffered
before they're yielded from the returned stream.
Note that the vectors returned from this iterator may not always have
capacity
elements. If the underlying stream ended and only a partial
vector was created, it'll be returned. Additionally if an error happens
from the underlying stream then the currently buffered items will be
yielded.
Errors are passed through the stream unbuffered.
This method is only available when the std
feature of this
library is activated, and it is activated by default.
Panics
This method will panic of capacity
is zero.
fn select<S>(self, other: S) -> Select<Self, S> where
S: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized,
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.
This combinator will attempt to pull items from both streams. Each stream will be polled in a round-robin fashion, and whenever a stream is ready to yield an item that item is yielded.
Error are passed through from either stream.
fn forward<S>(self, sink: S) -> Forward<Self, S> where
S: Sink<SinkItem = Self::Item>,
Self::Error: From<S::SinkError>,
Self: Sized,
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.
This future will drive the stream to keep producing items until it is exhausted, sending each item to the sink. It will complete once both the stream is exhausted, and the sink has received and flushed all items. Note that the sink is not closed.
Doing stream.forward(sink)
is roughly equivalent to
sink.send_all(stream)
. The returned future will exhaust all items from
self
, sending them all to sink
.
On completion, the pair (stream, sink)
is returned.
fn split(self) -> (SplitSink<Self>, SplitStream<Self>) where
Self: Sink + Sized,
Self: Sink + Sized,
Splits this Stream + Sink
object into separate Stream
and Sink
objects.
This can be useful when you want to split ownership between tasks, or
allow direct interaction between the two objects (e.g. via
Sink::send_all
).
This method is only available when the std
feature of this
library is activated, and it is activated by default.
fn inspect<F>(self, f: F) -> Inspect<Self, F> where
F: FnMut(&Self::Item),
Self: Sized,
F: FnMut(&Self::Item),
Self: Sized,
Do something with each item of this stream, afterwards passing it on.
This is similar to the Iterator::inspect
method in the standard
library where it allows easily inspecting each value as it passes
through the stream, for example to debug what's going on.
fn inspect_err<F>(self, f: F) -> InspectErr<Self, F> where
F: FnMut(&Self::Error),
Self: Sized,
F: FnMut(&Self::Error),
Self: Sized,
Do something with the error of this stream, afterwards passing it on.
This is similar to the Stream::inspect
method where it allows
easily inspecting the error as it passes through the stream, for
example to debug what's going on.
fn recover<E, F>(self, f: F) -> Recover<Self, E, F> where
F: FnMut(Self::Error) -> Option<Self::Item>,
Self: Sized,
F: FnMut(Self::Error) -> Option<Self::Item>,
Self: Sized,
Handle errors generated by this stream by converting them into
Option<Self::Item>
, such that a None
value terminates the stream.
Because it can never produce an error, the returned Recover
stream can
conform to any specific Error
type, including Never
.
fn left<B>(self) -> Either<Self, B> where
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized,
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized,
: use left_stream
instead
Wrap this stream in an Either
stream, making it the left-hand variant
of that Either
.
This can be used in combination with the right
method to write if
statements that evaluate to different streams in different branches.
fn right<B>(self) -> Either<B, Self> where
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized,
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized,
: use right_stream
instead
Wrap this stream in an Either
stream, making it the right-hand variant
of that Either
.
This can be used in combination with the left
method to write if
statements that evaluate to different streams in different branches.
fn left_stream<B>(self) -> Either<Self, B> where
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized,
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized,
Wrap this stream in an Either
stream, making it the left-hand variant
of that Either
.
This can be used in combination with the right_stream
method to write if
statements that evaluate to different streams in different branches.
fn right_stream<B>(self) -> Either<B, Self> where
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized,
B: Stream<Item = Self::Item, Error = Self::Error>,
Self: Sized,
Wrap this stream in an Either
stream, making it the right-hand variant
of that Either
.
This can be used in combination with the left_stream
method to write if
statements that evaluate to different streams in different branches.