I am getting error: Undefined class 'required'. when trying to use required keyword

Question

我收到错误：未定义 class 'required'。尝试使用必需关键字时。

这是代码示例：

class Field {
  final int id;
  final String name;
  final bool userEditable;
  final String title;
  Field({
    required this.id,
    this.name,
    this.userEditable,
    this.title,
  });
}

我已经在使用 flutter 的 @required 关键字，但我正在尝试切换到 dart 的新 required 关键字。

这里是 pubspec.yaml 的环境 sdk 行：

environment:
  sdk: ">=2.7.0 <3.0.0"

这里是 flutter --version 的输出：

Flutter 2.0.1 • channel stable • https://github.com/flutter/flutter.git
Framework • revision c5a4b4029c (2 weeks ago) • 2021-03-04 09:47:48 -0800
Engine • revision 40441def69
Tools • Dart 2.12.0

Answer 1

将您的最小 SDK 限制更新为 2.12.0。

environment:
  sdk: ">=2.12.0 <3.0.0"

I am getting error: Undefined class 'required'. when trying to use required keyword

I am getting error: Undefined class 'required'. when trying to use required keyword

dart

flutter

flutter-web