Event Bus

The EventBus is the primary way for modules to communicate without being tightly coupled. It supports both strongly-typed events and lightweight named signals.

Typed Events

Use Typed Events for critical business logic where you need compile-time safety.

1. Define an Event

Extend ModuleEvent and provide a sourceModuleId.

class UserLoggedInEvent extends ModuleEvent {
  final String userId;
  final String email;

  UserLoggedInEvent({
    required super.sourceModuleId,
    required this.userId,
    required this.email,
  });
}

2. Emit and Listen

// Emit
EventBus().emit(UserLoggedInEvent(
  sourceModuleId: 'auth',
  userId: '123',
  email: 'user@example.com',
));

// Listen
EventBus().on<UserLoggedInEvent>((event) {
  print('User ${event.email} logged in');
}, subscriberModuleId: 'home');

Named Signals

Signals are lightweight, dynamic messages identified by a string name.

// Emit
EventBus().emitSignal('cart.updated', data: {'count': 5}, sourceModuleId: 'cart');

// Listen
EventBus().onSignal('cart.updated', (data) {
  print('New count: ${data['count']}');
}, subscriberModuleId: 'header');

Middleware

You can intercept all events or signals to add global logic like logging or analytics.

EventBus().addMiddleware((event, next) {
  print('Log: ${event.runtimeType} from ${event.sourceModuleId}');
  next(event); // Continue the chain
});

Schema Validation (Optional)

For large teams, you can enforce the structure of signals at runtime.

EventSchemaValidator().registerSignalSchema(
  'user.register',
  MapSchema({
    'email': StringSchema(required: true),
    'age': NumberSchema(min: 18),
  }),
);