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avoid-duplicate-bloc-event-handlers

added in: 1.24.0
warning
⚙️
Free+

Warns when a bloc declares multiple event handlers for the same event.

Adding multiple handlers is usually a mistake and should not happen. Try changing the event name or creating a single method that combines multiple handlers.

⚙️ Config​

Set additional-methods (default is empty) to add additional methods used for listening to bloc events.

analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-duplicate-bloc-event-handlers:
        additional-methods:
          - customOn

Example​

❌ Bad:

class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0) {
    on<CounterIncrementEvent>(_handle);
    this.on<CounterIncrementEvent>(_handleCorrect); // LINT: Avoid multiple handlers for the same bloc event. Try refactoring this handler to only have one.
    on<CounterIncrementEvent>(_handleSync); // LINT: Avoid multiple handlers for the same bloc event. Try refactoring this handler to only have one.

    on<CounterDecrementEvent>((event, emit) => emit(state - 1));

    // LINT: Avoid multiple handlers for the same bloc event. Try refactoring this handler to only have one.
    on<CounterDecrementEvent>((event, emit) async {
      emit(state + 1);
      await Future.delayed(const Duration(seconds: 3));
      add(CounterDecrementEvent());
    });
  }
}

✅ Good:

class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0) {
    on<CounterIncrementEvent>(_handlerWithAllLogic);
    on<CounterDecrementEvent>(_handle);
  }
}