flutter - 分析使所需的构造函数出错

Question

'variable'是最终值，在声明时为其指定了值，因此无法将其设置为新值。请尝试删除其中一个初始化。
这是不断出现的错误。如何删除该错误？我需要一个http发布请求。

  Future<User> fetchUser() async {
  final response =
  await http.get('https://coronavirus-med.herokuapp.com/api/v1/auth/register');

  if (response.statusCode == 200) {
    // If the server did return a 200 OK response,
    // then parse the JSON.
    return User.fromJson(json.decode(response.body));
  } else {
    // If the server did not return a 200 OK response,
    // then throw an exception.
    throw Exception('Failed to load request');
  }
}

  class User{
  final String name = ' ';
  final String email = ' ';
  final String password = ' ';
  final String passwordConfirm = ' ';
  final String role = ' ';

  User({this.name, this.email, this.password, this.passwordConfirm, this.role});

  factory User.fromJson(Map<String, dynamic> json){
    return User(
      name: json['name'],
      email: json['email'],
      password: json['password'],
      passwordConfirm: json['passwordConfirm'],
      role: json['role'],
    );
  }
}

Answer 1

像这样更改您的User类

class User {
  final String name;
  final String email;
  final String password;
  final String passwordConfirm;
  final String role;

  User({
    String name,
    String email,
    String password,
    String passwordConfirm,
    String role,
  })  : this.name = name ?? ' ',
        this.email = email ?? ' ',
        this.password = password ?? ' ',
        this.passwordConfirm = passwordConfirm ?? ' ',
        this.role = role ?? ' ';

  factory User.fromJson(Map<String, dynamic> json) {
    return User(
      name: json['name'],
      email: json['email'],
      password: json['password'],
      passwordConfirm: json['passwordConfirm'],
      role: json['role'],
    );
  }
}