如何在 Flutter 中将字符串转换为对象？

Question

我有两个模型类 Employee 和 AdditionalDetails

class Employee{
  AdditionalDetails(this.uuid, this.additional_details);

  String uuid;
  String additional_details; 
}

class AdditionalDetails{
  AdditionalDetails(this.start, this.end, this.month);

  String start;
  String end;
  String month;

}

And I have a handler in which I am creating objects of AdditionalDetails and pushing into a list.


  List<Employee> list = new List<Employee>;
  String add1 = AdditionalDetails("start1", "end1", "dec").toString();
  String add2 = AdditionalDetails("start2", "end2", "jan").toString();
  list.add(1, add1);
  list.add(2, add2);

我在列表中显示这些项目，在单击每个项目时，我必须在对话框中显示其他详细信息。

我可以通过遍历列表来获取 uuid，但是在执行 json.decode(additional_details) 时，它给出了这个：

SyntaxError: Unexpected token I in JSON at position 0

如何从 additionalDetails 中获取开始、结束和月份属性？

Answer 1

我想这就是你想要的。

class Employee {
  Employee(this.uuid, this.additionalDetails);

  String uuid;
  String additionalDetails;
}

class AdditionalDetails {
  AdditionalDetails(
    this.start,
    this.end,
    this.month,
  );

  final String start;
  final String end;
  final String month;

  @override
  String toString() => '$start $end $month';
}

final list = <Employee>[];
final add1 = AdditionalDetails("start1", "end1", "dec").toString();
final add2 = AdditionalDetails("start2", "end2", "jan").toString();
list.add(Employee('1', add1));
list.add(Employee('2', add2));

更酷的方式：

class Employee {
  Employee({
    @required this.uuid,
    @required this.additionalDetails,
  });

  final String uuid;
  final AdditionalDetails additionalDetails;

  factory Employee.fromJson(Map<String, dynamic> json) => Employee(
        uuid: json["uuid"],
        additionalDetails: json["additionalDetails"],
      );

  Map<String, dynamic> toJson() => {
        "uuid": uuid,
        "additionalDetails": additionalDetails.toJson(),
      };
}

class AdditionalDetails {
  AdditionalDetails({
    @required this.start,
    @required this.end,
    @required this.month,
  });

  final String start;
  final String end;
  final String month;

  factory AdditionalDetails.fromJson(Map<String, dynamic> json) =>
      AdditionalDetails(
        start: json["start"],
        end: json["end"],
        month: json["month"],
      );

  Map<String, dynamic> toJson() => {
        "start": start,
        "end": end,
        "month": month,
      };
}

final list = <Employee>[];
final add1 = AdditionalDetails(start: "start1", end: "end1", month: "dec");
list.add(Employee(uuid: '1', additionalDetails: add1));

final json = add1.toJson(); // Map<String, dynamic>
final startFromJson = json['start'];

final object = AdditionalDetails.fromJson(json); // AdditionalDetails
final startFromObject = object.start;

Answer 2

如果你想用字符串而不是 jsondecode 创建一个对象，你应该使用 toJson 和 fromJson 函数：

class AdditionalDetails{
  AdditionalDetails(this.start, this.end, this.month);

  String start;
  String end;
  String month;

  AdditionalDetails.fromJson(Map<String, dynamic> json){

    this.start = json['start'];
    this.end = json['end'];
    this.month = json['month'];

  }

  Map<String, dynamic> toJson(){

    Map<String, dynamic> data = {};
    data['start'] = this.start;
    data['end'] = this.end;
    data['month'] = this.month;
    return data;

  }

}
List<Employee> list = new List<Employee>;
String add1 = AdditionalDetails("start1", "end1", "dec").toJson();
String add2 = AdditionalDetails("start2", "end2", "jan").toJson();
list.add(1, add1);
list.add(2, add2);

final object = AdditionalDetails.fromJson(add1);

如何在 Flutter 中将字符串转换为对象？

How to convert a String to Object in Flutter?

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