flutter_stream_notifiers

Description:

flutter stream notifiers

flutter_stream_notifiers #
Provides a bunch of special notifiers derived from Flutter's ValueNotifier or ChangeNotifier, that additionally streams a value or notifier itself on a change notification.
// TextEditingStreamController is a sub class of TextEditingController,
// that is a sub class of ValueNotifier.
final controller = TextEditingStreamController(text: 'a');
controller.stream.listen((TextEditingValue value) {
print(value.text); // prints a, b, c.
});
controller..text = 'b'..text = 'c';
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Available notifiers #

ValueStream streams a value on a change notification. It is for a sub class of ValueNotifier.
ChangeNotifierStream streams a notifier itself on a change notification. It is for a sub class of ChangeNotifier.

With ValueStream #



Sub class with ValueStream
Super class




ValueStreamNotifier
ValueNotifier


TextEditingStreamController
TextEditingController


ClipboardStatusStreamNotifier
ClipboardStatusNotifier


TransformationStreamController
TransformationController



With ChangeNotifierStream #



Sub class with ChangeNotifierStream
Super class




ChangeStreamNotifier
ChangeNotifier


ScrollStreamController
ScrollController


FocusStreamNode
FocusNode


FocusStreamManager
FocusManager


PageStreamController
PageController




This package will eventually provide most of the classes corresponding to kinds of ChangeNotifier or ValueNotifier in Flutter framework.
Current Status #
(Flutter version 1.21.0).
Providing stream notifiers corresponding to classes of:

ValueNotifier: completed
ChangeNotifier: NOT completed

Extending third party packages. #
For keeping this package's dependency as minimum as possible, this package will only provide the notifiers whose super classes are available in Flutter framework.
For a third party package that has a class derived from ValueNotifier or ChangeNotifier, one can create a notifier from them with ValueStream or ChangeNotifierStream.
It should be fairly easy since it's just about applying corresponding mixin.
class DerivedValueStreamNotifier<T> = DerivedValueNotifier<T> with ValueStream<T>;
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The examples from this package's implementation.
/// A [TextEditingController] with [ValueStream].
class TextEditingStreamController = TextEditingController
with ValueStream<TextEditingValue>;
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/// A [ScrollController] with [ChangeNotifierStream].
class ScrollStreamController = ScrollController
with ChangeNotifierStream<ScrollController>;
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Features #
All constructors are derived from a super class #
// TextEditingStreamController is a TextEditingController with ValueStream mixin.
// It derives all constructors from TextEditingController.
final controller = TextEditingStreamController(text: 'a');
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A latest value will be delivered on listen immediately #
Unlike addListener, a latest value is delivered on listen.
final controller = TextEditingStreamController(text: 'a');
controller.stream.listen(print); // prints a, b.
controller.addListener(() {
print(controller.text); // prints b.
})
controller.text = 'b';
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Internally, addListener on listening a stream, removeListener on canceling a stream subscription #
final controller = TextEditingStreamController(text: 'a');
final subscription = controller.stream.listen(print); // addListener() internally.
subscription.cancel(); // removeListener internally.
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Multiple listeners are allowed #
final controller = TextEditingStreamController(text: 'a');
controller.stream.listen(print); // prints a.
controller.stream.listen(print); // prints a.
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This package leverages MultiStream supported at Dart 2.9.
With ChangeNotifierStream, a notifier itself will be delivered #
class DerivedChangeStreamNotifier
extends ChangeStreamNotifier<DerivedChangeStreamNotifier> {
DerivedChangeStreamNotifier(this._count);

int _count;
int get count => _count;
void increment() {
_count++;
notifyListeners();
}
}

notifier = DerivedChangeStreamNotifier(0);
notifier.stream.listen((notifier) {
print(notifier.count); // prints 0, 1.
print(notifier is DerivedChangeStreamNotifier) // prints true, true.
});
notifier.increment();
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All streams are closed on dispose #
final controller = TextEditingStreamController(text: 'a');
controller.stream.listen(null, onDone: () {
prints('done!'); // prints done!.
});
controller.dispose();
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A new Stream of a notifier that has been disposed of, is closed immediately
final controller = TextEditingStreamController(text: 'a');
controller.dispose();
controller.stream.listen(null, onDone: () {
prints('done!'); // prints done!.
});
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No runtime FlutterError occurs when listening a stream of a notifier that has been disposed of.
Features and bugs #
Please file feature requests and bugs at the issue tracker.