StateBroadcaster

main.dart

import 'dart:async';

void main() {
  final broadcaster = StateBroadcaster();
}

class StateBroadcaster  {
  final _sinkMap = <Type, StreamController<dynamic>>{};

  void notify<T>(T value) {
    setMapIfNeeded();
    _sinkMap[T]?.add(value);
  }

  StreamSubscription<T> listen<T>(void Function(T) onData) {
    setMapIfNeeded();
    return _sinkMap[T].stream.listen(onData);
  }

  void setMapIfNeeded<T>() {
    _sinkMap[T] ??= StreamController<T>.broadcast();
  }
}