flutter 1.升级2.X在模型类中序列化JSON报错Non-nullable instance field ‘title’ must be initialized.

flutter 1.升级2.X在模型类中序列化JSON报错

Non-nullable instance field ‘title‘ must be initialized.
Try adding an initializer expression,
or add a field initializer in this constructor, or mark it ‘late‘.

修改方案--添加late

原有代码

class Autogenerated {
List<Result> result;
Autogenerated({this.result});
Autogenerated.fromJson(Map<String, dynamic> json) {
if (json[‘result‘] != null) {
result = new List<Result>();
json[‘result‘].forEach((v) {
result.add(new Result.fromJson(v));
});
}
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
if (this.result != null) {
data[‘result‘] = this.result.map((v) => v.toJson()).toList();
}
return data;
}
}
class Result {
String sId;
String title;
String status;
String pic;
String url;
Result({this.sId, this.title, this.status, this.pic, this.url});
Result.fromJson(Map<String, dynamic> json) {
sId = json[‘_id‘];
title = json[‘title‘];
status = json[‘status‘];
pic = json[‘pic‘];
url = json[‘url‘];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data[‘_id‘] = this.sId;
data[‘title‘] = this.title;
data[‘status‘] = this.status;
data[‘pic‘] = this.pic;
data[‘url‘] = this.url;
return data;
}
}

修改后的

class Autogenerated {
late List<Result> result;
Autogenerated({required this.result});
Autogenerated.fromJson(Map<String, dynamic> json) {
if (json[‘result‘] != null) {
result = [];
json[‘result‘].forEach((v) {
result.add(new Result.fromJson(v));
});
}
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
if (this.result != null) {
data[‘result‘] = this.result.map((v) => v.toJson()).toList();
}
return data;
}
}
class Result {
late String sId;
late String title;
late String status;
late String pic;
late String url;
Result(
{required this.sId,
required this.title,
required this.status,
required this.pic,
required this.url});
Result.fromJson(Map<String, dynamic> json) {
sId = json[‘_id‘];
title = json[‘title‘];
status = json[‘status‘];
pic = json[‘pic‘];
url = json[‘url‘];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data[‘_id‘] = this.sId;
data[‘title‘] = this.title;
data[‘status‘] = this.status;
data[‘pic‘] = this.pic;
data[‘url‘] = this.url;
return data;
}
}

flutter 1.升级2.X在模型类中序列化JSON报错Non-nullable instance field 'title' must be initialized.

原文：https://www.cnblogs.com/sugartang/p/15302924.html