StreamController class - dart:async library (original) (raw)
StreamController<T> class abstract interface
A controller with the stream it controls.
This controller allows sending data, error and done events on its stream.
This class can be used to create a simple stream that others can listen on, and to push events to that stream.
It's possible to check whether the stream is paused or not, and whether it has subscribers or not, as well as getting a callback when either of these change.
Example:
final streamController = StreamController(
onPause: () => print('Paused'),
onResume: () => print('Resumed'),
onCancel: () => print('Cancelled'),
onListen: () => print('Listens'),
);
streamController.stream.listen(
(event) => print('Event: $event'),
onDone: () => print('Done'),
onError: (error) => print(error),
);
To check whether there is a subscriber on the stream, use hasListener.
var hasListener = streamController.hasListener; // true
To send data events to the stream, use add or addStream.
streamController.add(999);
final stream = Stream<int>.periodic(
const Duration(milliseconds: 200), (count) => count * count).take(4);
await streamController.addStream(stream);
To send an error event to the stream, use addError or addStream.
streamController.addError(Exception('Issue 101'));
await streamController.addStream(Stream.error(Exception('Issue 404')));
To check whether the stream is closed, use isClosed.
var isClosed = streamController.isClosed; // false
To close the stream, use close.
await streamController.close();
isClosed = streamController.isClosed; // true
Implemented types
- StreamSink<T>
Implementers
Available extensions
Constructors
StreamController({void onListen()?, void onPause()?, void onResume()?, FutureOr<void> onCancel()?, bool sync = false})
A controller with a stream that supports only one single subscriber.
factory
StreamController.broadcast({void onListen()?, void onCancel()?, bool sync = false})
A controller where stream can be listened to more than once.
factory
Properties
A future which is completed when the stream controller is done sending events.
no setteroverride
The hash code for this object.
no setterinherited
Whether there is a subscriber on the Stream.
no setter
Whether the stream controller is closed for adding more events.
no setter
Whether the subscription would need to buffer events.
no setter
onCancel ↔ FutureOr<void> Function()?
The callback which is called when the stream is canceled.
getter/setter pair
onListen ↔ void Function()?
The callback which is called when the stream is listened to.
getter/setter pair
onPause ↔ void Function()?
The callback which is called when the stream is paused.
getter/setter pair
onResume ↔ void Function()?
The callback which is called when the stream is resumed.
getter/setter pair
A representation of the runtime type of the object.
no setterinherited
sink → StreamSink<T>
Returns a view of this object that only exposes the StreamSink interface.
no setter
The stream that this controller is controlling.
no setter
Methods
add(T event)→ void
Sends a data event.
override
addError(Object error, [StackTrace? stackTrace])→ void
Sends or enqueues an error event.
override
addStream(Stream<T> source, {bool? cancelOnError})→ Future
Receives events from source and puts them into this controller's stream.
override
Closes the stream.
override
noSuchMethod(Invocation invocation)→ dynamic
Invoked when a nonexistent method or property is accessed.
inherited
rejectErrors()→ StreamSink<T>
Available on StreamSink<T>, provided by the StreamSinkExtensions extension
Returns a StreamSink that forwards to this but rejects errors.
A string representation of this object.
inherited
transform<S>(StreamSinkTransformer<S, T> transformer)→ StreamSink<S>
Available on StreamSink<T>, provided by the StreamSinkExtensions extension
Transforms a StreamSink using transformer.
Operators
operator ==(Object other)→ bool
The equality operator.
inherited