到 json 映射模型，其中包含子模型列表

问题描述

我是 flutter dev 的新手，正在尝试将模型转换为 json 字符串以传递给 api 调用。

当我尝试使用 RegistrationRequest.ToJson 函数时，出现此错误

type '_InternalLinkedHashMap<String,dynamic>' is not a subtype of type 'String'

我认为它无法正确转换 userImages 列表，并且不太确定如何进行转换。任何帮助将不胜感激

这里是我调用函数的地方

var serialisedBodycom = RegistrationRequest.toJson();
      var serialisedBody = jsonEncode(serialisedBodycom);

我有一个模型叫做 注册请求

    import 'UserGender.dart';
import 'UserImage.dart';

class RegistrationRequest {
  String email;
  String password;
  String msisdn;
  UserGender gender;
  UserGender matchGender;
  List<UserImage> userImages;

  RegistrationRequest(
      {this.email,this.password,this.msisdn,this.gender,this.matchGender,this.userImages});
  RegistrationRequest.Empty();

  RegistrationRequest.fromJson(Map<String,dynamic> json)
      : email = json['email'],password = json['password'],msisdn = json['msisdn'],gender = json['gender'],matchGender = json['matchGender'],userImages = json['userImages'];

  Map<String,dynamic> toJson() {
    return {
      'email': email ?? '','password': password ?? '','MSISDN': msisdn ?? '','Gender': gender ?? UserGender.Unknown,'MatchGender': matchGender ?? UserGender.Unknown,'UserImages': userImages ?? new List<UserImage>()
    };
  }
}

其中包含一个 UserImage 列表

    class UserImage {
  String base64;
  String fileName;
  bool isMainProfilePicture;
  String contentType;

  UserImage(
      this.base64,this.fileName,this.isMainProfilePicture,this.contentType);
  UserImage.Empty();
  UserImage.fromJson(Map<dynamic,dynamic> json)
      : base64 = json['base64'],fileName = json['fileName'],isMainProfilePicture = json['isMainProfilePicture'],contentType = json['contentType'];

  Map<dynamic,dynamic> toJson() => {
        'base64': base64,'fileName': fileName,'isMainProfilePicture': isMainProfilePicture,'contentType': contentType
      };
}

解决方法

我想出的最终答案如下

RegistrationRequest.fromJson(Map<String,dynamic> json) => RegistrationRequest(
        email: json["email"],password: json["password"],msisdn: json["msisdn"],gender: json["gender"],matchGender: json["matchGender"],userImages: List<UserImage>.from(json["userImages"].map((x) => UserImage.fromJson(x))),);

    Map<String,dynamic> toJson() => {
        "email": email,"password": password,"msisdn": msisdn,"gender": gender,"matchGender": matchGender,"userImages": List<dynamic>.from(userImages.map((x) => x.toJson())),