Dart Map to Class

Question

是否有将地图转换为用户定义类对象的标准方法。

在python中你可以做MyClass（** map），它基本上将地图展开为类的构造函数的命名参数。

任何指针/帮助都将不胜感激。

Answer 1

您也可以使用named constructor手动完成此操作，例如：

import 'package:flutter/material.dart';

Map myMap = {"Users": [

  {"Name": "Mark", "Email": "mark@email"},


  {"Name": "Rick", "Email": "rick@email"},
]
};

class MyData {
  String name;
  String email;

  MyData.fromJson(Map json){
    this.name = json["Name"];
    this.email = json ["Email"];
  }
}

class UserList extends StatelessWidget {
  MyData data;

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(title: new Text("User List"),),
        body:
        new ListView.builder(
            shrinkWrap: true,
            itemCount: myMap["Users"].length,
            itemBuilder: (BuildContext context, int index) {
              data = new MyData.fromJson(myMap["Users"][index]);
              return new Text("${data.name} ${data.email}");
            })
    );
  }
}

Answer 2

You can use Function.apply。我做了gist来测试链接答案

Answer 3

采用这种方法，调用代码可以具有类型安全性，street和city字段的自动完成功能以及编译时异常。如果您输入错误或将字段视为int而不是Strings，则应用将无法编译，而不会在运行时崩溃。

Address.fromJson()构造函数，用于从地图结构构造新的User实例。

一种toJson()方法，它将User实例转换为地图。

class Address {
  String street;
  String city;

  Address(this.street, this.city);

  Address.fromJson(Map<String, dynamic> json)
      : street = json['street'],
        city = json['city'];

  Map<String, dynamic> toJson() =>
      {
        'citstreety': street,
        'city': city,
      };
}


List<Address>  getAddressList(){

  Map myMap = {"address": [
    {"street": "Marine Lines", "city": "Mumbai"},
    {"street": "Main Road", "city": "Delhi"},
  ]
  };

  var data = myMap["address"];
  List<Address> addressModelList = [];
  for (var u in data) {
    Address address =
    Address.fromJson(u);
    addressModelList.add(address);
  }
  return addressModelList;
}