json - 未处理的异常: 'String'类型不是 'int'类型的子类型，即使数据中没有整数

Question

我正在使用POST请求从数据库获取数据，并且以JSON格式检索数据。这是数据示例:

[
{
    "course_name": "Calculus & Analytical Geometry",
    "batch_name": "FA16-BCS-B16-B"
},
{
    "course_name": "COURSE 3",
    "batch_name": "FA16-BCS-B16-B"
},
{
    "course_name": "COURSE 4",
    "batch_name": "FA16-BCS-B16-B"
},
{
    "course_name": "COURSE 5",
    "batch_name": "FA16-BCS-B16-B"
},
{
    "course_name": "COURSE 6",
    "batch_name": "FA16-BCS-B16-B"
},
{
    "course_name": "Object Oriented Programming",
    "batch_name": "FA16-BCS-B16-B"
}
]

我有以下解析类。

class TeacherHomeData {
final String course_name;
final int batch_name;

TeacherHomeData({this.course_name, this.batch_name});

factory TeacherHomeData.fromJson(Map<String, dynamic> json) {
return TeacherHomeData(
  course_name: json['course_name'],
  batch_name: json['batch_name'],
);
}

Map<String, dynamic> toMap() =>
  {"course_name": course_name, "batch_name": batch_name};
}

我正在像这样获取和解析数据:

ppUtils.getStringFromPref("teacher_id").then((teacher_id) async {
  final data = await http
      .post(AppUtils.teacherHomeLink, body: {"teacher_id": teacher_id});
  var responseBody = data.body;
 print(responseBody);
  final parsed = json.decode(data.body).cast<Map<String, dynamic>>();

  List<TeacherHomeData> parentSigninList = parsed
      .map<TeacherHomeData>((json) => TeacherHomeData.fromJson(json))
      .toList();

它引发以下错误。

E/flutter (19272): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: type 'String' is not a subtype of type 'int'
E/flutter (19272): #0      new TeacherHomeData.fromJson (package:attendance_system/JSONConverterClasses/TeacherHomeData.dart:11:23)
E/flutter (19272): #1      _Teacher_HomeState.jamoo.<anonymous closure>.<anonymous closure> (package:attendance_system/src/TeacherHome.dart:69:59)
E/flutter (19272): #2      MappedListIterable.elementAt (dart:_internal/iterable.dart:417:29)
E/flutter (19272): #3      ListIterable.toList (dart:_internal/iterable.dart:221:19)
E/flutter (19272): #4      _Teacher_HomeState.jamoo.<anonymous closure>     (package:attendance_system/src/TeacherHome.dart:70:12)
E/flutter (19272): <asynchronous suspension>

我找不到异常背后的逻辑。我的数据中没有 int值，为什么它会引发此异常。

Answer 1

您在模型中将batch_name用作整数，而json文件中的字符串则是一个字符串，这就是它显示解析错误的原因。试试这个:

class TeacherHomeData {
final String course_name;
final String batch_name;

TeacherHomeData({this.course_name, this.batch_name});

factory TeacherHomeData.fromJson(Map<String, dynamic> json) {
return TeacherHomeData(
  course_name: json['course_name'],
  batch_name: json['batch_name'],
);
}

Map<String, dynamic> toMap() =>
  {"course_name": course_name, "batch_name": batch_name};
}