Question 75660 in Flutter Question posted in
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Unsupported operation: Cannot add to an unmodifiable list unsing Bloc – Flutter

i am using bloc to add and remove from am list..

my bloc state is like this,

@freezed
class InterestActionState with _$InterestActionState {
  factory InterestActionState({
    required bool isSubmitting,
    required List<String> selectedInterest,
    required Option<Either<InterestFailure, Unit>>
        intrestFailureOrSuccessOption,
  }) = Initial;

  factory InterestActionState.initial() => InterestActionState(
        isSubmitting: false,
        selectedInterest: <String>[],
        intrestFailureOrSuccessOption: none(),
      );

  const InterestActionState._();
}

also i am adding to the list like this

  void addInterestToMyList(
    AddMyList event,
    Emitter<InterestActionState> emit,
  ) {
    emit(state.copyWith(
        selectedInterest: state.selectedInterest..add(event.selectedInterest)));

}

and to Remove from the List is

 void removeInterestToMyList(
    RemoveFromList event,
    Emitter<InterestActionState> emit,
  ) {
    emit(state.copyWith(
        selectedInterest: state.selectedInterest
          ..remove(event.selectedInterest)));
  }

but i keep getting flutter: Unsupported operation: Cannot add to an unmodifiable list

Tags:

2

Answers


  1. 0

    change your code into:

      void addInterestToMyList(
    AddMyList event,
    Emitter<InterestActionState> emit,
  ) {
    emit(state.copyWith(
        selectedInterest: [...state.selectedInterest, event.selectedInterest]));

    and to remove it, create a new lazy list without editing the original one:

    emit(state.copyWith(
    selectedInterest: state.selectedInterest.where((e) => e != event.selectedInterest).toList()));

    this should solve your issue

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  2. 0

    state.selectedInterest must be unmodifiable, and remove and add modify the list in place (it modifies the list and doesn’t create a copy).

    You can create a copy yourself using .toList():

    Add:

     void addInterestToMyList(
    AddMyList event,
    Emitter<InterestActionState> emit,
  ) {
    emit(state.copyWith(
        selectedInterest: state.selectedInterest.toList()..add(event.selectedInterest)));

    Remove:

    void removeInterestToMyList(
    RemoveFromList event,
    Emitter<InterestActionState> emit,
  ) {
    emit(state.copyWith(
        selectedInterest: state.selectedInterest.toList()
          ..remove(event.selectedInterest)));
  }
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