flutter - 为什么json序列化器要建模类错误？

Question

json

{
"status":1,
"error":"error",
"data":{"id":10000,"email":"xxx@test.com"}
}

数据字段是任意类型的数据
models.dart

import 'package:flutter/material.dart';

class User {
  int id;
  String email;

  User({
    @required this.id,
    @required this.email,
  });
}

class Response<T> {
  final int status;
  final String error;
  final T data;

  const Response({
    this.status,
    this.error,
    this.data,
  });

  factory Response.formJson(Map<String, dynamic> json) {
    return Response(
      status: json["status"] as int,
      error: json["error"] as String,
      data: (json["data"] as T),
    );
  }
}

user.dart

class User {
  int id;
  String email;

  User({
    this.id,
     this.email,
  });
}

码

Response resp = Response<User>.formJson(json);
print(resp.status);
print(resp.error);
print(resp.data);

异常(exception)
未处理的异常:类型'_InternalLinkedHashMap '不是类型转换中'用户'类型的子类型
怎么处理呢？
是否需要再次序列化？

Answer 1

json["data"]本质上是Map<String, dynamic>的一种。您的User对象没有隐式转换，因此您必须将该Map显式转换为User。为此，您可以执行基本上与Response的工厂构造函数相同的操作。
对User类的更改:

class User {
  int id;
  String email;

  User({
    @required this.id,
    @required this.email,
  });

  factory User.fromJson(Map<String, dynamic> json) {
    return User(
      id: json["id"],
      email: json["email"],
    );
  }
}

对 Response.formJson的更改:

factory Response.formJson(Map<String, dynamic> json) {
    return Response(
      status: json["status"] as int,
      error: json["error"] as String,
      data: User.fromJson(json["data"]), //or T.fromJson is that is a required capability and all your possible T's will have a fromJson constructor
    );
  }