bloc + combineLatest

main.dart

import 'dart:async';

import 'package:bloc/bloc.dart';
import 'package:rxdart/rxdart.dart';

enum CounterEvent { increment }

class CounterBloc extends Bloc<CounterEvent, int> {
  @override
  int get initialState => 0;

  @override
  Stream<int> mapEventToState(
    CounterEvent event,
  ) async* {
    switch (event) {
      case CounterEvent.increment:
        yield state + 1;
        break;
    }
  }
}

void main() async {
  final counterBlocA = CounterBloc();
  final counterBlocB = CounterBloc();

  Rx.combineLatest2(counterBlocA, counterBlocB, ((a, b) {
    return [a, b];
  })).listen((combinedStates) {
    final stateA = combinedStates.first;
    final stateB = combinedStates.last;

    print('($stateA, $stateB)');
  });

  Timer.periodic(
    Duration(seconds: 1),
    (_) => counterBlocA.add(CounterEvent.increment),
  );
  Timer.periodic(
    Duration(seconds: 2),
    (_) => counterBlocB.add(CounterEvent.increment),
  );
}