Mapping JSON into Class Objects

Question

I am trying to map my JSON file into a class object, and then update the cards based on the newly received JSON.

My JSON structure is like this

 {
          


        

Answer 1

I created some useful library for this using reflection called json_parser which is available at pub.

https://github.com/gi097/json_parser

You can add the following to your dependencies.yaml:

dependencies:
  json_parser: 0.1.1
  build_runner: 0.8.3

Then the json can be parsed using:

DataClass instance = JsonParser.parseJson<DataClass>(json);

Follow the README.md for more instructions.

Answer 2

The best solution I've found is this medium post

Which converts the Json to dart very easily

import 'package:json_annotation/json_annotation.dart';

part 'post_model.g.dart';

@JsonSerializable()
class PostModel {
  int userId;
  int id;
  String title;
  String body;
  PostModel(this.userId, this.id, this.title, this.body);
  factory PostModel.fromJson(Map<String, dynamic> json) => _$PostModelFromJson(json);
  Map<String, dynamic> toJson() => _$PostModelToJson(this);
}

Answer 3

class CardInfo {
  //Constructor
  String id;
  String description;
  String role;
  int score;

  CardInfo.fromJson(Map json) {
    this.id = json['id'];
    this.description = json['description'];
    this.role = json['Role'];
    this.score = json['score'];
  }
}

var ci = new CardInfo.fromJson(myJson); 

You can use source generation tools like https://github.com/dart-lang/source_gen https://pub.dartlang.org/packages/json_serializable to generate the serialization and deserialization code for you.

If you prefer using immutable classes https://pub.dartlang.org/packages/built_value is a good bet.

Answer 4

this pkg can help you convert JSON to a class instance. https://www.npmjs.com/package/class-converter

import { property, toClass } from 'class-convert';

class UserModel {
  @property('i')
  id: number;

  @property()
  name: string;
}

const userRaw = {
  i: 1234,
  name: 'name',
};

// use toClass to convert plain object to class
const userModel = toClass(userRaw, UserModel);
// you will get a class, just like below one
{
  id: 1234,
  name: 'name',
}

Answer 5

If you want to get your JSON from a url do as follows:

import 'dart:convert';

_toObject() async {
  var url = 'YourJSONurl';
  var httpClient  = createHttpClient();
  var response =await httpClient.get(url);
  Map cardInfo = JSON.decode(response.body);
  var ci = new CardInfo.fromJson(cardInfo);
}

Please refer to the main answer if you want to know how to setup your class so that your JSON fields can be mapped to it. It is very helpful.