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Behavior distinct
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| /* | |
| * Behavior distinct | |
| * https://gist.github.com/PlugFox/d2afc6bd33c138e9ef0e6c74f405c779 | |
| * https://dartpad.dev?id=d2afc6bd33c138e9ef0e6c74f405c779 | |
| * Mike Matiunin <[email protected]>, 27 August 2024 | |
| */ | |
| // ignore_for_file: avoid_print | |
| import 'dart:async'; | |
| void main() { | |
| final subject = BehaviorSubject.seed(0)..add(1); | |
| final subscription = _subscribeDistinctPrint(subject, fix: true); | |
| print('Current value: ${subject.value}\n' | |
| 'Emits:'); | |
| subject | |
| ..add(1) | |
| ..add(2) | |
| ..add(3) | |
| ..add(4) | |
| ..close(); | |
| Timer(Duration.zero, () { | |
| subscription.cancel(); | |
| subject.close(); | |
| }); | |
| } | |
| StreamSubscription<T> _subscribeDistinctPrint<T>( | |
| BehaviorSubject<T> subject, { | |
| bool fix = false, | |
| }) { | |
| if (fix) { | |
| final value = subject.value; | |
| return () async* { | |
| yield value; | |
| yield* subject.stream; | |
| }() | |
| .distinct() | |
| .skip(1) | |
| .listen(print); | |
| } else { | |
| return subject._controller.stream.distinct().listen(print); | |
| } | |
| } | |
| final class BehaviorSubject<T> implements Sink<T> { | |
| BehaviorSubject.seed(this._value); | |
| final StreamController<T> _controller = StreamController<T>(); | |
| Stream<T> get stream => _controller.stream; | |
| T _value; | |
| T get value => _value; | |
| @override | |
| void add(T event) => _controller.add(_value = event); | |
| @override | |
| void close() => _controller.close(); | |
| } |
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