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emit-new-bloc-state-instances

added in: 1.25.0
warning
Free+

Warns when an emit invocation receives the existing state instead of a newly created instance.

Passing existing state objects can create issues when the state is not properly updating.

Example​

❌ Bad:

abstract class CounterEvent {}

class CounterDecrementEvent extends CounterEvent {}

class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0) {
    on<CounterDecrementEvent>((event, emit) async {
      // LINT: Avoid emitting existing state objects as it can lead to missing state updates. Try creating a new instance instead.
      emit(state);
    });
  }
}

✅ Good:

class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0) {
    on<CounterDecrementEvent>((event, emit) async {
      emit(state + 1);
      emit(state.copyWith(...));
    });
  }
}

Additional Resources​