Dart 语言相关答案

【问题标题】：Dart Language RelatedDart 语言相关
【发布时间】：2023-02-04 20:50:58
【问题描述】：

我试图为问题创建一个类，以便我可以在我的测验应用程序的 main.dart 文件中使用它，但我遇到了一些错误。请告诉我为什么会出现这些错误，我该如何解决？

类问题：

class Question {
  String questionText;
  bool questionAnswer;

  Question({String q, bool a}) {
    questionText = q;
    questionAnswer = a;
  }
}

错误：

Non-nullable instance field 'questionAnswer' must be initialized.
Non-nullable instance field 'questionText' must be initialized.
The parameter 'q' can't have a value of 'null' because of its type, but the implicit default value is 'null'.
The parameter 'a' can't have a value of 'null' because of its type, but the implicit default value is 'null'.

Image of Errors here.

【问题讨论】：

标签： flutter dart

【解决方案1】：

问题是关于 null-safey，您需要使字段可为空，late 或在构造函数中添加 required。

class Question {
  late String questionText;
  late bool questionAnswer;

  Question({required String q, required bool a}) {
    questionText = q;
    questionAnswer = a;
  }
}

class Question {
   String questionText;
   bool questionAnswer;

  Question({required this.questionAnswer, required this.questionText});
}

查找更多关于-null-safety

【讨论】：