flutter_stream_notifiers 0.3.0-nullsafety.0

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.

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';

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>;

The examples from this package's implementation.

/// A [TextEditingController] with [ValueStream].
class TextEditingStreamController = TextEditingController
    with ValueStream<TextEditingValue>;

/// A [ScrollController] with [ChangeNotifierStream].
class ScrollStreamController = ScrollController
    with ChangeNotifierStream<ScrollController>;

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');

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';

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.

Multiple listeners are allowed

final controller = TextEditingStreamController(text: 'a');
controller.stream.listen(print); // prints a.
controller.stream.listen(print); // prints a.

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();

All streams are closed on dispose

final controller = TextEditingStreamController(text: 'a');
controller.stream.listen(null, onDone: () {
  prints('done!'); // prints done!.
});
controller.dispose();

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!.
});

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.