list - 如何为列表中的单个项目(而不是整个列表)编写 setter？

Question

我的模型中有一个包含 bool 列表的类。在我的 UI 中，我想通过 setter 在列表中的单个项目中设置 bool 状态(这样我也可以保存它)。我无法弄清楚语法(或者这是否是一件有效的事情)。

   ///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();
  }

我知道我在这里遗漏了一些明显的东西，非常感谢任何帮助

Answer 1

get 和 set 函数不能接受任何参数。最简单的方法是使用普通函数:

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

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

另一种选择是将 _questionsAnswered 从 List 更改为实现 operator [] 的自定义类(以获取元素)和operator []=(设置一个元素)，然后你可以让他们做任何你想做的事情。