How do you write a setter for a single item in a list (not the whole list)?

Question

I have a class in my model that includes a list of bool. From my UI I want to set the bool state in just a single item in the list via a setter (so that I can also save it). I can't figure out the syntax (or whether this is a valid thing to do).

   ///This is OK
   set notificationDismissed(bool notificationDismissed){
     _notificationDismissed = notificationDismissed;
     saveParameterBoolean(_notificationDismissedKey, 
  _notificationDismissed);
    }
  bool get notificationDismissed => _notificationDismissed;


  ///This is OK too
  List<bool> get questionsAnswered => _questionsAnswered;
  set questionsAnswered(List<bool> questionsAnswered){
    _questionsAnswered = questionsAnswered;
    for(int i=0; i<_questionAnsweredParamKeys.length; i++ ){
      saveParameterBoolean(_questionAnsweredParamKeys[i], 
  _questionsAnswered[i]);
    }
    updateState();
  }

  ///This is not OK !!!! but should show what I want to do
  List<bool> get questionsAnswered[index] => _questionsAnswered[index];
  set questionsAnswered[index](bool questionsAnswered[index]){
    _questionsAnswered[index] = questionsAnswered[index];
    saveParameterBoolean(_questionAnsweredParamKeys[index], 
  _questionsAnswered[index]);
    updateState();
  }

I know I'm missing something obvious here, any help greatly appreciated

Solution

get and set functions can't take any arguments. The simplest approach would be to use normal functions:

bool getQuestionsAnswered(int index) =>  _questionsAnswered[index];

void setQuestionsAnswered(int index, bool value) {
  _questionsAnswered[index] = value;
  saveParameterBoolean(_questionAnsweredParamKeys[index], _questionsAnswered[index]);
  updateState();
}

Another alternative would be to change _questionsAnswered from a List to a custom class that implements operator [] (to get an element) and operator []= (to set an element), and then you could make them do whatever you want.

Comments

[Chris Bennett]

Awesome, thank you, I'll just implement a function and move on :-)

[Kasandrop]

That is not true! set functions take arguments in dart but only one