CombineLatestStream<T, R> class

Merges the given Streams into one Stream sequence by using the combiner function whenever any of the source stream sequences emits an item.

The Stream will not emit until all Streams have emitted at least one item.

If the provided streams is empty, the resulting sequence completes immediately without emitting any items and without any calls to the combiner function.

Interactive marble diagram

Basic Example

This constructor takes in an Iterable<Stream<T>> and outputs a Stream<Iterable<T>> whenever any of the values change from the source stream. This is useful with a dynamic number of source streams!

CombineLatestStream.list<String>([
  Stream.fromIterable(['a']),
  Stream.fromIterable(['b']),
  Stream.fromIterable(['C', 'D'])])
.listen(print); //prints ['a', 'b', 'C'], ['a', 'b', 'D']

Example with combiner

If you wish to combine the list of values into a new object before you

CombineLatestStream(
  [
    Stream.fromIterable(['a']),
    Stream.fromIterable(['b']),
    Stream.fromIterable(['C', 'D'])
  ],
  (values) => values.last
)
.listen(print); //prints 'C', 'D'

Example with a specific number of Streams

If you wish to combine a specific number of Streams together with proper types information for the value of each Stream, use the combine2 - combine9 operators.

CombineLatestStream.combine2(
  Stream.fromIterable([1]),
  Stream.fromIterable([2, 3]),
  (a, b) => a + b,
)
.listen(print); // prints 3, 4

Inheritance

Object
Stream<R>
StreamView<R>
CombineLatestStream

Available extensions

StreamExtensions

Constructors

CombineLatestStream(Iterable<Stream<T>> streams, R combiner(List<T> values)): Constructs a Stream that observes an Iterable of Stream and builds a List containing all latest events emitted by the provided Iterable of Stream. The combiner maps this List into a new event of type R

Properties

first → Future<R>: The first element of this stream.
no setterinherited
hashCode → int: The hash code for this object.
no setterinherited
isBroadcast → bool: Whether this stream is a broadcast stream.
no setterinherited
isEmpty → Future<bool>: Whether this stream contains any elements.
no setterinherited
last → Future<R>: The last element of this stream.
no setterinherited
length → Future<int>: The number of elements in this stream.
no setterinherited
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited
single → Future<R>: The single element of this stream.
no setterinherited

Methods

any(bool test(R element)) → Future<bool>: Checks whether test accepts any element provided by this stream.
inherited
asBroadcastStream({void onListen(StreamSubscription<R> subscription)?, void onCancel(StreamSubscription<R> subscription)?}) → Stream<R>: Returns a multi-subscription stream that produces the same events as this.
inherited
asyncExpand<E>(Stream<E>? convert(R event)) → Stream<E>: Transforms each element into a sequence of asynchronous events.
inherited
asyncMap<E>(FutureOr<E> convert(R event)) → Stream<E>: Creates a new stream with each data event of this stream asynchronously mapped to a new event.
inherited
cast<R>() → Stream<R>: Adapt this stream to be a Stream<R>.
inherited
contains(Object? needle) → Future<bool>: Returns whether needle occurs in the elements provided by this stream.
inherited
distinct([bool equals(R previous, R next)?]) → Stream<R>: Skips data events if they are equal to the previous data event.
inherited
drain<E>([E? futureValue]) → Future<E>: Discards all data on this stream, but signals when it is done or an error occurred.
inherited
elementAt(int index) → Future<R>: Returns the value of the indexth data event of this stream.
inherited
every(bool test(R element)) → Future<bool>: Checks whether test accepts all elements provided by this stream.
inherited
expand<S>(Iterable<S> convert(R element)) → Stream<S>: Transforms each element of this stream into a sequence of elements.
inherited
firstWhere(bool test(R element), {R orElse()?}) → Future<R>: Finds the first element of this stream matching test.
inherited
fold<S>(S initialValue, S combine(S previous, R element)) → Future<S>: Combines a sequence of values by repeatedly applying combine.
inherited
forEach(void action(R element)) → Future<void>: Executes action on each element of this stream.
inherited
handleError(Function onError, {bool test(dynamic error)?}) → Stream<R>: Creates a wrapper Stream that intercepts some errors from this stream.
inherited
join([String separator = ""]) → Future<String>: Combines the string representation of elements into a single string.
inherited
lastWhere(bool test(R element), {R orElse()?}) → Future<R>: Finds the last element in this stream matching test.
inherited
listen(void onData(R value)?, {Function? onError, void onDone()?, bool? cancelOnError}) → StreamSubscription<R>: Adds a subscription to this stream.
inherited
map<S>(S convert(R event)) → Stream<S>: Transforms each element of this stream into a new stream event.
inherited
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
inherited
pipe(StreamConsumer<R> streamConsumer) → Future: Pipes the events of this stream into streamConsumer.
inherited
reduce(R combine(R previous, R element)) → Future<R>: Combines a sequence of values by repeatedly applying combine.
inherited
singleWhere(bool test(R element), {R orElse()?}) → Future<R>: Finds the single element in this stream matching test.
inherited
skip(int count) → Stream<R>: Skips the first count data events from this stream.
inherited
skipWhile(bool test(R element)) → Stream<R>: Skip data events from this stream while they are matched by test.
inherited
take(int count) → Stream<R>: Provides at most the first count data events of this stream.
inherited
takeWhile(bool test(R element)) → Stream<R>: Forwards data events while test is successful.
inherited
timeout(Duration timeLimit, {void onTimeout(EventSink<R> sink)?}) → Stream<R>: Creates a new stream with the same events as this stream.
inherited
toList() → Future<List<R>>: Collects all elements of this stream in a List.
inherited
toSet() → Future<Set<R>>: Collects the data of this stream in a Set.
inherited
toString() → String: A string representation of this object.
inherited
transform<S>(StreamTransformer<R, S> streamTransformer) → Stream<S>: Applies streamTransformer to this stream.
inherited
where(bool test(R event)) → Stream<R>: Creates a new stream from this stream that discards some elements.
inherited
withInitialValue(Future<T> value) → Stream<T>: Available on Stream<T>, provided by the StreamExtensions extension

Operators

operator ==(Object other) → bool: The equality operator.
inherited

Static Methods

combine2<A, B, R>(Stream<A> streamOne, Stream streamTwo, R combiner(A a, B b)) → CombineLatestStream<dynamic, R>: Constructs a CombineLatestStream from a pair of Streams where combiner is used to create a new event of type R, based on the latest events emitted by the provided Streams.
combine3<A, B, C, R>(Stream<A> streamA, Stream streamB, Stream<C> streamC, R combiner(A a, B b, C c)) → CombineLatestStream<dynamic, R>: Constructs a CombineLatestStream from 3 Streams where combiner is used to create a new event of type R, based on the latest events emitted by the provided Streams.
combine4<A, B, C, D, R>(Stream<A> streamA, Stream streamB, Stream<C> streamC, Stream<D> streamD, R combiner(A a, B b, C c, D d)) → CombineLatestStream<dynamic, R>: Constructs a CombineLatestStream from 4 Streams where combiner is used to create a new event of type R, based on the latest events emitted by the provided Streams.
combine5<A, B, C, D, E, R>(Stream<A> streamA, Stream streamB, Stream<C> streamC, Stream<D> streamD, Stream<E> streamE, R combiner(A a, B b, C c, D d, E e)) → CombineLatestStream<dynamic, R>: Constructs a CombineLatestStream from 5 Streams where combiner is used to create a new event of type R, based on the latest events emitted by the provided Streams.
combine6<A, B, C, D, E, F, R>(Stream<A> streamA, Stream streamB, Stream<C> streamC, Stream<D> streamD, Stream<E> streamE, Stream<F> streamF, R combiner(A a, B b, C c, D d, E e, F f)) → CombineLatestStream<dynamic, R>: Constructs a CombineLatestStream from 6 Streams where combiner is used to create a new event of type R, based on the latest events emitted by the provided Streams.
combine7<A, B, C, D, E, F, G, R>(Stream<A> streamA, Stream streamB, Stream<C> streamC, Stream<D> streamD, Stream<E> streamE, Stream<F> streamF, Stream<G> streamG, R combiner(A a, B b, C c, D d, E e, F f, G g)) → CombineLatestStream<dynamic, R>: Constructs a CombineLatestStream from 7 Streams where combiner is used to create a new event of type R, based on the latest events emitted by the provided Streams.
combine8<A, B, C, D, E, F, G, H, R>(Stream<A> streamA, Stream streamB, Stream<C> streamC, Stream<D> streamD, Stream<E> streamE, Stream<F> streamF, Stream<G> streamG, Stream<H> streamH, R combiner(A a, B b, C c, D d, E e, F f, G g, H h)) → CombineLatestStream<dynamic, R>: Constructs a CombineLatestStream from 8 Streams where combiner is used to create a new event of type R, based on the latest events emitted by the provided Streams.
combine9<A, B, C, D, E, F, G, H, I, R>(Stream<A> streamA, Stream streamB, Stream<C> streamC, Stream<D> streamD, Stream<E> streamE, Stream<F> streamF, Stream<G> streamG, Stream<H> streamH, Stream streamI, R combiner(A a, B b, C c, D d, E e, F f, G g, H h, I i)) → CombineLatestStream<dynamic, R>: Constructs a CombineLatestStream from 9 Streams where combiner is used to create a new event of type R, based on the latest events emitted by the provided Streams.
list<T>(Iterable<Stream<T>> streams) → CombineLatestStream<T, List<T>>: Constructs a CombineLatestStream using a default combiner, which simply yields a List of all latest events emitted by the provided Iterable of Stream.