How do BLoC to BLoC communication patterns work, letting one given BLoC properly react to a genuinely separate other BLoC's own emitted state changes, such as a cart BLoC properly reacting whenever a genuinely separate authentication BLoC's own state actually changes?

BLoC to BLoC communication typically involves one particular BLoC properly subscribing directly to a genuinely separate other BLoC's own state stream, often within its own constructor, and reacting appropriately whenever that particular other BLoC emits a genuinely new state, such as a CartBloc properly clearing its own entire cart state the very instant an AuthBloc's own emitted state indicates that a user has genuinely just logged out, and while this particular pattern is genuinely quite useful, it should generally still be used somewhat sparingly, since excessive direct coupling between several separate individual BLoCs can meaningfully begin to reduce their own overall individual testability and genuine independence from one another.

class CartBloc extends Bloc<CartEvent, CartState> {
  CartBloc(AuthBloc authBloc) : super(CartState.empty()) {
    authBloc.stream.listen((authState) {
      if (authState is LoggedOut) add(ClearCart());
    });
  }
}