examplepub/sub

pubsub.dart

import 'dart:async';

void main() {
 X.eventStream.stream.listen(print);
 Y.eventStream.stream.listen(print);
 Main.eventStream.add(XEvent("came from X"));
}

class Event {}

class XEvent extends Event{
  XEvent(this.field);
  final String field;
  
}

class YEvent extends Event{
  YEvent(this.field);
  final String field;
  
  @override
  String toString() => "YEvent(field: $field)";
}

class Main {
  static final eventStream = StreamController<Event>()..stream.forEach(
 (e) {
   if(e is XEvent) Y.eventStream.add(YEvent(e.field));
 });
  
}

class X {
  static final eventStream = StreamController<Event>();
}

class Y {
  static final eventStream = StreamController<Event>();
}