FromCallableStream<T> class Null safety

Returns a Stream that, when listening to it, calls a function you specify and then emits the value returned from that function.

If result from invoking callable function:

  • Is a Future: when the future completes, this stream will fire one event, either data or error, and then close with a done-event.
  • Is a T: this stream emits a single data event and then completes with a done event.

By default, a FromCallableStream is a single-subscription Stream. However, it's possible to make them reusable. This Stream is effectively equivalent to one created by (() async* { yield await callable() }()) or (() async* { yield callable(); }()).

ReactiveX doc

Example

FromCallableStream(() => 'Value').listen(print); // prints Value

FromCallableStream(() async {
  await Future<void>.delayed(const Duration(seconds: 1));
  return 'Value';
}).listen(print); // prints Value
Inheritance
Available Extensions

Constructors

FromCallableStream(FutureOr<T> callable(), {bool reusable = false})
Construct a Stream that, when listening to it, calls a function you specify and then emits the value returned from that function. reusable indicates whether this Stream can be listened to multiple times or not.

Properties

callable FutureOr<T> Function()
A function will be called at subscription time.
final
first Future<T>
The first element of this stream. [...]
read-only, inherited
hashCode int
The hash code for this object. [...]
read-only, inherited
isBroadcast bool
Whether this stream is a broadcast stream.
read-only, override
isEmpty Future<bool>
Whether this stream contains any elements. [...]
read-only, inherited
last Future<T>
The last element of this stream. [...]
read-only, inherited
length Future<int>
The number of elements in this stream. [...]
read-only, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited
single Future<T>
The single element of this stream. [...]
read-only, inherited

Methods

any(bool test(T element)) Future<bool>
Checks whether test accepts any element provided by this stream. [...]
inherited
asBroadcastStream({void onListen(StreamSubscription<T> subscription)?, void onCancel(StreamSubscription<T> subscription)?}) Stream<T>
Returns a multi-subscription stream that produces the same events as this. [...]
inherited
asyncExpand<E>(Stream<E>? convert(T event)) Stream<E>
Transforms each element into a sequence of asynchronous events. [...]
inherited
asyncMap<E>(FutureOr<E> convert(T 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(T previous, T next)?]) Stream<T>
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<T>
Returns the value of the indexth data event of this stream. [...]
inherited
every(bool test(T element)) Future<bool>
Checks whether test accepts all elements provided by this stream. [...]
inherited
expand<S>(Iterable<S> convert(T element)) Stream<S>
Transforms each element of this stream into a sequence of elements. [...]
inherited
firstWhere(bool test(T element), {T orElse()?}) Future<T>
Finds the first element of this stream matching test. [...]
inherited
fold<S>(S initialValue, S combine(S previous, T element)) Future<S>
Combines a sequence of values by repeatedly applying combine. [...]
inherited
forEach(void action(T element)) Future
Executes action on each element of this stream. [...]
inherited
handleError(Function onError, {bool test(dynamic error)?}) Stream<T>
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(T element), {T orElse()?}) Future<T>
Finds the last element in this stream matching test. [...]
inherited
listen(void onData(T event)?, {Function? onError, void onDone()?, bool? cancelOnError}) StreamSubscription<T>
Adds a subscription to this stream. [...]
override
map<S>(S convert(T event)) Stream<S>
Transforms each element of this stream into a new stream event. [...]
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
inherited
pipe(StreamConsumer<T> streamConsumer) Future
Pipes the events of this stream into streamConsumer. [...]
inherited
reduce(T combine(T previous, T element)) Future<T>
Combines a sequence of values by repeatedly applying combine. [...]
inherited
singleWhere(bool test(T element), {T orElse()?}) Future<T>
Finds the single element in this stream matching test. [...]
inherited
skip(int count) Stream<T>
Skips the first count data events from this stream. [...]
inherited
skipWhile(bool test(T element)) Stream<T>
Skip data events from this stream while they are matched by test. [...]
inherited
take(int count) Stream<T>
Provides at most the first count data events of this stream. [...]
inherited
takeWhile(bool test(T element)) Stream<T>
Forwards data events while test is successful. [...]
inherited
timeout(Duration timeLimit, {void onTimeout(EventSink<T> sink)?}) Stream<T>
Creates a new stream with the same events as this stream. [...]
inherited
toList() Future<List<T>>
Collects all elements of this stream in a List. [...]
inherited
toSet() Future<Set<T>>
Collects the data of this stream in a Set. [...]
inherited
toString() String
A string representation of this object. [...]
inherited
transform<S>(StreamTransformer<T, S> streamTransformer) Stream<S>
Applies streamTransformer to this stream. [...]
inherited
where(bool test(T event)) Stream<T>
Creates a new stream from this stream that discards some elements. [...]
inherited

Operators

operator ==(Object other) bool
The equality operator. [...]
inherited