[DART]- Check if a value exists in a list of objects

Question

I've got an Abstract class named QuizzAnswer and I've a class named QuizzAnswerMCQ which extends QuizzAnswer class.

abstract class QuizzAnswer extends Equatable {}

 class QuizzAnswerMCQ extends QuizzAnswer {
  String optionId;
  bool isSelected;

 QuizzAnswerMCQ({required this.optionId, required this.isSelected});

   @override
   List<Object?> get props => [optionId, isSelected];

   Map<String, dynamic> toJson() => {
      "option_id": optionId,
       "is_selected": isSelected,
    };
 }

and I've got a list which is of type QuizzAnswerMCQ

List<QuizzAnswerMCQ> quizAnswerList=[];

and I add items to the list

quizAnswerList.add(QuizzAnswerMCQ(
      optionId: event.optionId, isSelected: event.optionValue));

what I want to do is to check if the optionId is already there in the list or not so I wrote this,

if(quizAnswerList.map((item) => item.optionId).contains(event.optionId)){
    print ('EXISTTTTSSSSS');
  }else{
    print('DOESNT EXISTTTT');
  }

Even though the optionId is there,I still get the output 'DOESNT EXISTTTT'.Please help!!!

Answer 1

You can use firstWhere like this

result = quizAnswerList.firstWhere((item) => item.optionId == your_id);

or checking from other List

result = quizAnswerList.firstWhere((item) => otherList.contains(item));

then

    if(result.length > 0){
      print ('');
    }else{
      print(');
    }

Official doc here