Json 如何定义一个属性既可以为null的模型,也可以是Dart中的另一个模型
我正在构建一个颤振应用程序,在定义模型时遇到了一些问题。我有一个模型,它有一些属性。其中一个属性可以是null或另一个模型Json 如何定义一个属性既可以为null的模型,也可以是Dart中的另一个模型,json,flutter,dart,model,Json,Flutter,Dart,Model,我正在构建一个颤振应用程序,在定义模型时遇到了一些问题。我有一个模型,它有一些属性。其中一个属性可以是null或另一个模型 import 'package:proef/models/worked_time.dart'; class Shift { String uuid; DateTime start_at; DateTime end_at; String title; String comment; WorkedTime worked_time; Shift(
import 'package:proef/models/worked_time.dart';
class Shift {
String uuid;
DateTime start_at;
DateTime end_at;
String title;
String comment;
WorkedTime worked_time;
Shift(
{this.uuid,
this.start_at,
this.end_at,
this.title,
this.comment,
this.worked_time});
factory Shift.fromData(Map<String, dynamic> parsedJson) {
print(parsedJson);
return Shift(
uuid: parsedJson['uuid'],
start_at: DateTime.parse(parsedJson['start_at']).toLocal(),
end_at: DateTime.parse(parsedJson['end_at']).toLocal(),
title: parsedJson['title'],
comment: parsedJson['comment'],
worked_time: parsedJson['worked_time'] == null
? null
: parsedJson['worked_time']);
}
}
没有工作时间的JSON
[
{
"uuid": "706f40e7-d57c-470c-9023-b0c58e2c7c3a",
"start_at": "2020-09-01T08:00:00.000000Z",
"end_at": "2020-09-01T16:00:00.000000Z",
"title": "Test",
"comment": "Test",
"worked_time": {
"uuid": "6e73b4aa-d6e1-41f7-86cb-09745d2db033",
"comment": "Test",
"status": 0,
"break": 0,
"start_at": "2020-09-01T08:00:00.000000Z",
"end_at": "2020-09-01T16:00:00.000000Z",
"took_break": 0
}
}
]
[
{
"uuid": "706f40e7-d57c-470c-9023-b0c58e2c7c3a",
"start_at": "2020-09-01T08:00:00.000000Z",
"end_at": "2020-09-01T16:00:00.000000Z",
"title": "Test",
"comment": "Test",
"worked_time": null
}
]
你能试试这个型号吗
// To parse this JSON data, do
//
// final shift = shiftFromJson(jsonString);
import 'dart:convert';
List<Shift> shiftFromJson(String str) => List<Shift>.from(json.decode(str).map((x) => Shift.fromJson(x)));
String shiftToJson(List<Shift> data) => json.encode(List<dynamic>.from(data.map((x) => x.toJson())));
class Shift {
Shift({
this.uuid,
this.startAt,
this.endAt,
this.title,
this.comment,
this.workedTime,
});
String uuid;
DateTime startAt;
DateTime endAt;
String title;
String comment;
WorkedTime workedTime;
factory Shift.fromJson(Map<String, dynamic> json) => Shift(
uuid: json["uuid"] == null ? null : json["uuid"],
startAt: json["start_at"] == null ? null : DateTime.parse(json["start_at"]),
endAt: json["end_at"] == null ? null : DateTime.parse(json["end_at"]),
title: json["title"] == null ? null : json["title"],
comment: json["comment"] == null ? null : json["comment"],
workedTime: json["worked_time"] == null ? null : WorkedTime.fromJson(json["worked_time"]),
);
Map<String, dynamic> toJson() => {
"uuid": uuid == null ? null : uuid,
"start_at": startAt == null ? null : startAt.toIso8601String(),
"end_at": endAt == null ? null : endAt.toIso8601String(),
"title": title == null ? null : title,
"comment": comment == null ? null : comment,
"worked_time": workedTime == null ? null : workedTime.toJson(),
};
}
class WorkedTime {
WorkedTime({
this.uuid,
this.comment,
this.status,
this.workedTimeBreak,
this.startAt,
this.endAt,
this.tookBreak,
});
String uuid;
String comment;
int status;
int workedTimeBreak;
DateTime startAt;
DateTime endAt;
int tookBreak;
factory WorkedTime.fromJson(Map<String, dynamic> json) => WorkedTime(
uuid: json["uuid"] == null ? null : json["uuid"],
comment: json["comment"] == null ? null : json["comment"],
status: json["status"] == null ? null : json["status"],
workedTimeBreak: json["break"] == null ? null : json["break"],
startAt: json["start_at"] == null ? null : DateTime.parse(json["start_at"]),
endAt: json["end_at"] == null ? null : DateTime.parse(json["end_at"]),
tookBreak: json["took_break"] == null ? null : json["took_break"],
);
Map<String, dynamic> toJson() => {
"uuid": uuid == null ? null : uuid,
"comment": comment == null ? null : comment,
"status": status == null ? null : status,
"break": workedTimeBreak == null ? null : workedTimeBreak,
"start_at": startAt == null ? null : startAt.toIso8601String(),
"end_at": endAt == null ? null : endAt.toIso8601String(),
"took_break": tookBreak == null ? null : tookBreak,
};
}
//要解析此JSON数据,请执行以下操作
//
//最终移位=shiftFromJson(jsonString);
导入“dart:convert”;
List-shiftFromJson(String-str)=>List.from(json.decode(str.map)(x)=>Shift.fromJson(x));
字符串shiftToJson(List data)=>json.encode(List.from(data.map)((x)=>x.toJson());
班次{
移位({
这个.uuid,
这是startAt,
这个.endAt,,
这个名字,
这句话,,
这个工作时间,
});
字符串uuid;
日期时间起始时间;
日期时间结束;
字符串标题;
字符串注释;
工作时间工作时间;
工厂Shift.fromJson(映射json)=>Shift(
uuid:json[“uuid”]==null?null:json[“uuid”],
startAt:json[“start_at”]==null?null:DateTime.parse(json[“start_at”]),
endAt:json[“end_at”]==null?null:DateTime.parse(json[“end_at”]),
title:json[“title”]==null?null:json[“title”],
comment:json[“comment”]==null?null:json[“comment”],
workedTime:json[“worked_time”]==null?null:workedTime.fromJson(json[“worked_time”]),
);
映射到JSON()=>{
“uuid”:uuid==null?null:uuid,
“start_at”:startAt==null?null:startAt.toIso8601String(),
“end_at”:endAt==null?null:endAt.toIso8601String(),
“title”:title==null?null:title,
“注释”:注释==空?空:注释,
“工作时间”:workedTime==null?null:workedTime.toJson(),
};
}
上课时间{
工作时间({
这个.uuid,
这句话,,
这个,身份,,
这个,工作时间休息,
这是startAt,
这个.endAt,,
这是tookBreak,
});
字符串uuid;
字符串注释;
智力状态;
int工作时间间隔;
日期时间起始时间;
日期时间结束;
int tookBreak;
factory WorkedTime.fromJson(映射json)=>WorkedTime(
uuid:json[“uuid”]==null?null:json[“uuid”],
comment:json[“comment”]==null?null:json[“comment”],
status:json[“status”]==null?null:json[“status”],
workedTimeBreak:json[“break”]==null?null:json[“break”],
startAt:json[“start_at”]==null?null:DateTime.parse(json[“start_at”]),
endAt:json[“end_at”]==null?null:DateTime.parse(json[“end_at”]),
tookBreak:json[“take_break”]==null?null:json[“take_break”],
);
映射到JSON()=>{
“uuid”:uuid==null?null:uuid,
“注释”:注释==空?空:注释,
“状态”:状态==空?空:状态,
“break”:workedTimeBreak==null?null:workedTimeBreak,
“start_at”:startAt==null?null:startAt.toIso8601String(),
“end_at”:endAt==null?null:endAt.toIso8601String(),
“take_break”:tookBreak==null?null:tookBreak,
};
}
编译器不会抱怨将动态
变量分配给类型化变量,因为检查是在运行时完成的。因此,你可以写:
void main() {
dynamic value = "something";
String string = value; // ok, value holds a String; runtime is fine
WorkedTime time = value; // evaluated at runtime; exception
}
此问题出现在Shift
的工厂构造函数中:
worked_time: parsedJson['worked_time'] == null
? null // true: can assign null to WorkedTime
: parsedJson['worked_time']); // false: assign dynamic to WorkedTime
您正试图将值为parsedJson['worked\u time']
的dynamic
类型分配给您的WorkedTime
类型。这些是不兼容的类型。相反,您必须使用WorkedTime
的构造函数从JSON映射构造实例。以下是您的问题的简化示例:
class WorkedTime {
String comment;
WorkedTime.fromData(Map<String, dynamic> json) : comment = json['comment'];
}
class Shift {
String uuid;
WorkedTime worked_time;
Shift.fromData(Map<String, dynamic> json)
: uuid = json['uuid'],
// next line causes the exception; cannot assign dynamic to WorkedTime
// fix: use WorkedTime.fromData(json['worked_time'])
worked_time = json['worked_time'];
}
你能展示你的json吗?这样我就可以建议你一个工厂代码,把json添加到描述中。提前谢谢!
worked_time: parsedJson['worked_time'] == null
? null // true: can assign null to WorkedTime
: parsedJson['worked_time']); // false: assign dynamic to WorkedTime
class WorkedTime {
String comment;
WorkedTime.fromData(Map<String, dynamic> json) : comment = json['comment'];
}
class Shift {
String uuid;
WorkedTime worked_time;
Shift.fromData(Map<String, dynamic> json)
: uuid = json['uuid'],
// next line causes the exception; cannot assign dynamic to WorkedTime
// fix: use WorkedTime.fromData(json['worked_time'])
worked_time = json['worked_time'];
}
class Shift {
String uuid;
WorkedTime worked_time;
Shift.fromData(Map<String, dynamic> json)
: uuid = json['uuid'],
worked_time = json['worked_time'] != null
? WorkedTime.fromData(json['worked_time']) // parse WorkedTime's json
: null;
}
void main() {
const json = <String, dynamic>{
'uuid': '706f40e7-d57c-470c-9023-b0c58e2c7c3a',
'worked_time': <String, dynamic>{'comment': 'on break'}
};
final shift = Shift.fromData(json);
// check that shift.worked_time is not null, etc.
print(shift.worked_time.comment);
}