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Description:

replay bloc

An extension to package:bloc which adds automatic undo and redo support to bloc and cubit states. Built to work with package:bloc.
Learn more at bloclibrary.dev!

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Creating a ReplayCubit #
class CounterCubit extends ReplayCubit<int> {
CounterCubit() : super(0);

void increment() => emit(state + 1);
}
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Using a ReplayCubit #
void main() {
final cubit = CounterCubit();

// trigger a state change
cubit.increment();
print(cubit.state); // 1

// undo the change
cubit.undo();
print(cubit.state); // 0

// redo the change
cubit.redo();
print(cubit.state); // 1
}
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ReplayCubitMixin #
If you wish to be able to use a ReplayCubit in conjuction with a different type of cubit like HydratedCubit, you can use the ReplayCubitMixin.
class CounterCubit extends HydratedCubit<int> with ReplayCubitMixin {
CounterCubit() : super(0);

void increment() => emit(state + 1);
void decrement() => emit(state - 1);

@override
int fromJson(Map<String, dynamic> json) => json['value'] as int;

@override
Map<String, int> toJson(int state) => {'value': state};
}
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Creating a ReplayBloc #
class CounterEvent extends ReplayEvent {}

class CounterIncrementPressed extends CounterEvent {}

class CounterDecrementPressed extends CounterEvent {}

class CounterBloc extends ReplayBloc<CounterEvent, int> {
CounterBloc() : super(0) {
on<CounterIncrementPressed>((event, emit) => emit(state + 1));
on<CounterDecrementPressed>((event, emit) => emit(state - 1));
}
}
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Using a ReplayBloc #
void main() {
// trigger a state change
final bloc = CounterBloc()..add(CounterIncrementPressed());

// wait for state to update
await bloc.stream.first;
print(bloc.state); // 1

// undo the change
bloc.undo();
print(bloc.state); // 0

// redo the change
bloc.redo();
print(bloc.state); // 1
}
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ReplayBlocMixin #
If you wish to be able to use a ReplayBloc in conjuction with a different type of cubit like HydratedBloc, you can use the ReplayBlocMixin.
sealed class CounterEvent with ReplayEvent {}

final class CounterIncrementPressed extends CounterEvent {}

final class CounterDecrementPressed extends CounterEvent {}

class CounterBloc extends HydratedBloc<CounterEvent, int> with ReplayBlocMixin {
CounterBloc() : super(0) {
on<CounterIncrementPressed>((event, emit) => emit(state + 1));
on<CounterDecrementPressed>((event, emit) => emit(state - 1));
}

@override
int fromJson(Map<String, dynamic> json) => json['value'] as int;

@override
Map<String, int> toJson(int state) => {'value': state};
}
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Dart Versions #

Dart 2: >= 2.12

Maintainers #

Felix Angelov