Flutter移动电商实战 --（22）JSON解析和复杂数据模型转换技巧

json转Model类

创建model文件夹，在里面新建category.dart类

主要根据这个json来分析我们要做成类的样子

{
  "code": "0",
  "message": "success",
  "data": [
    {
      "mallCategoryId": "4",
      "mallCategoryName": "白酒",
      "bxMallSubDto": [
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          "mallSubId": "2c9f6c94621970a801626a35cb4d0175",
          "mallCategoryId": "4",
          "mallSubName": "名酒",
          "comments": ""
        },
        {
          "mallSubId": "2c9f6c94621970a801626a363e5a0176",
          "mallCategoryId": "4",
          "mallSubName": "宝丰",
          "comments": ""
        },
        {
          "mallSubId": "2c9f6c94621970a801626a3770620177",
          "mallCategoryId": "4",
          "mallSubName": "北京二锅头",
          "comments": ""
        },
        {
          "mallSubId": "2c9f6c94679b4fb10167f7cc035c15a8",
          "mallCategoryId": "4",
          "mallSubName": "大明",
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          "mallCategoryId": "4",
          "mallSubName": "杜康",
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          "mallSubName": "顿丘",
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          "mallSubName": "汾酒",
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          "mallSubName": "枫林",
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          "mallSubName": "高粱酒",
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          "mallSubName": "古井",
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        },
        {
          "mallSubId": "2c9f6c946449ea7e01647dd4f6a40049",
          "mallCategoryId": "2c9f6c946449ea7e01647cd108b60020",
          "mallSubName": "常温酸奶",
          "comments": ""
        },
        {
          "mallSubId": "2c9f6c946449ea7e01647dd51ab7004a",
          "mallCategoryId": "2c9f6c946449ea7e01647cd108b60020",
          "mallSubName": "低温奶",
          "comments": ""
        }
      ],
      "comments": null,
      "image": "http://images.baixingliangfan.cn/firstCategoryPicture/20190131/20190131170151_9234.png"
    },
    {
      "mallCategoryId": "2c9f6c946449ea7e01647ccfddb3001e",
      "mallCategoryName": "休闲零食",
      "bxMallSubDto": [
        {
          "mallSubId": "2c9f6c946449ea7e01647dc51d93003c",
          "mallCategoryId": "2c9f6c946449ea7e01647ccfddb3001e",
          "mallSubName": "方便食品",
          "comments": ""
        },
        {
          "mallSubId": "2c9f6c946449ea7e01647dd204dc0040",
          "mallCategoryId": "2c9f6c946449ea7e01647ccfddb3001e",
          "mallSubName": "面包糕点",
          "comments": ""
        },
        {
          "mallSubId": "2c9f6c946449ea7e01647dd22f760041",
          "mallCategoryId": "2c9f6c946449ea7e01647ccfddb3001e",
          "mallSubName": "糖果巧克力",
          "comments": ""
        },
        {
          "mallSubId": "2c9f6c946449ea7e01647dd254530042",
          "mallCategoryId": "2c9f6c946449ea7e01647ccfddb3001e",
          "mallSubName": "膨化食品",
          "comments": ""
        },
        {
          "mallSubId": "2c9f6c94679b4fb10167f7fa132b15e7",
          "mallCategoryId": "2c9f6c946449ea7e01647ccfddb3001e",
          "mallSubName": "坚果炒货",
          "comments": null
        },
        {
          "mallSubId": "2c9f6c94679b4fb10167f7f4bfc415e2",
          "mallCategoryId": "2c9f6c946449ea7e01647ccfddb3001e",
          "mallSubName": "肉干豆干",
          "comments": null
        },
        {
          "mallSubId": "2c9f6c94679b4fb10167f7f5027a15e3",
          "mallCategoryId": "2c9f6c946449ea7e01647ccfddb3001e",
          "mallSubName": "饼干",
          "comments": null
        },
        {
          "mallSubId": "2c9f6c94679b4fb10167f7f530fd15e4",
          "mallCategoryId": "2c9f6c946449ea7e01647ccfddb3001e",
          "mallSubName": "冲调",
          "comments": null
        },
        {
          "mallSubId": "2c9f6c94683a6b0d016846b49436003b",
          "mallCategoryId": "2c9f6c946449ea7e01647ccfddb3001e",
          "mallSubName": "休闲水果",
          "comments": null
        }
      ],
      "comments": null,
      "image": "http://images.baixingliangfan.cn/firstCategoryPicture/20190131/20190131170200_7553.png"
    },
    {
      "mallCategoryId": "2c9f6c946449ea7e01647cd08369001f",
      "mallCategoryName": "粮油调味",
      "bxMallSubDto": [
        {
          "mallSubId": "2c9f6c946449ea7e01647dd2e8270043",
          "mallCategoryId": "2c9f6c946449ea7e01647cd08369001f",
          "mallSubName": "油/粮食",
          "comments": ""
        },
        {
          "mallSubId": "2c9f6c946449ea7e01647dd31bca0044",
          "mallCategoryId": "2c9f6c946449ea7e01647cd08369001f",
          "mallSubName": "调味品",
          "comments": ""
        },
        {
          "mallSubId": "2c9f6c946449ea7e01647dd35a980045",
          "mallCategoryId": "2c9f6c946449ea7e01647cd08369001f",
          "mallSubName": "酱菜罐头",
          "comments": ""
        }
      ],
      "comments": null,
      "image": "http://images.baixingliangfan.cn/firstCategoryPicture/20181212/20181212115842_9733.png"
    },
    {
      "mallCategoryId": "2c9f6c9468a85aef016925444ddb271b",
      "mallCategoryName": "积分商品",
      "bxMallSubDto": [
        
      ],
      "comments": null,
      "image": "http://images.baixingliangfan.cn/firstCategoryPicture/20190225/20190225232703_9950.png"
    }
  ]
}

class CategoryBigModel{
  String mallCategoryId;//类别编号
  String mallCategoryName;//类别名称
}

comments这个字段都是null值。

所以在创建了的时候 我们直接用null来表示

我们上面只做了一个模型类：CategoryBigModel

在json里面是有多个CategoryBigModel类的。就是一个list的数据。CategoryBigListModel

使用我们定义的model，和model的list集合

我们要输出大类的名称

输出我们的类别

快速生成我们的dart类，数据模型

https://javiercbk.github.io/json_to_dart/

把所有的json复制过来，自动生成类

最终代码

category.dart

class CategoryBigModel{
  String mallCategoryId;//类别编号
  String mallCategoryName;//类别名称
  List<dynamic> bxMallSubDto;//不知道具体模型就用dynamic类型
  Null comments;
  String image;

  //构造方法
  CategoryBigModel({
    this.mallCategoryId,
    this.mallCategoryName,
    this.bxMallSubDto,
    this.comments,
    this.image
  });
  //工厂类的构造方法,就是我常用的实例化对象模式，好处是我们调用这个类的时候不用再使用new关键字了
  //相当于java里面的多态，用起来和我们的静态方法是一样的
  factory CategoryBigModel.formJson(dynamic json){
    return CategoryBigModel(
      mallCategoryId:json['mallCategoryId'],
      mallCategoryName:json['mallCategoryName'],
      bxMallSubDto:json['bxMallSubDto'],
      comments:json['comments'],
      image:json['image']
    );
  }
}

//列表的model
class CategoryBigListModel{
  List<CategoryBigModel> data;
  CategoryBigListModel(this.data);

  factory CategoryBigListModel.fromJson(List json){
    return CategoryBigListModel(
      json.map((i)=>CategoryBigModel.formJson((i))).toList()
    );
  }
}

category_page.dart

import 'package:flutter/material.dart';
import '../service/service_method.dart';
import 'dart:convert';
import '../model/category.dart';

class CategoryPage extends StatefulWidget {
  @override
  _CategoryPageState createState() => _CategoryPageState();
}

class _CategoryPageState extends State<CategoryPage> {
  @override
  Widget build(BuildContext context) {
    _getCategory();
    return Container(
      child:Center(
        child: Text('分类页面'),
      )
    );
  }

  void _getCategory() async{
    await request('getCategory').then((val){
      var data=json.decode(val.toString());
      //print(data);
      CategoryBigListModel list= CategoryBigListModel.fromJson(data['data']);
      list.data.forEach((item)=>print(item.mallCategoryName));
    });
  }
}

//

class CategoryBigModel{
  String mallCategoryId;//类别编号
  String mallCategoryName;//类别名称
  List<dynamic> bxMallSubDto;//不知道具体模型就用dynamic类型
  Null comments;
  String image;

  //构造方法
  CategoryBigModel({
    this.mallCategoryId,
    this.mallCategoryName,
    this.bxMallSubDto,
    this.comments,
    this.image
  });
  //工厂类的构造方法,就是我常用的实例化对象模式，好处是我们调用这个类的时候不用再使用new关键字了
  //相当于java里面的多态，用起来和我们的静态方法是一样的
  factory CategoryBigModel.formJson(dynamic json){
    return CategoryBigModel(
      mallCategoryId:json['mallCategoryId'],
      mallCategoryName:json['mallCategoryName'],
      bxMallSubDto:json['bxMallSubDto'],
      comments:json['comments'],
      image:json['image']
    );
  }
}

//列表的model
class CategoryBigListModel{
  List<CategoryBigModel> data;
  CategoryBigListModel(this.data);

  factory CategoryBigListModel.fromJson(List json){
    return CategoryBigListModel(
      json.map((i)=>CategoryBigModel.formJson((i))).toList()
    );
  }
}

.