Parse JSON to Dart Object in Flutter

First of all, install the HTTP package in Flutter, and after that import HTTP package like the below code:

import 'package:http/http.dart' as HTTP;

And then you must create a map or a list:

  Map<int, FavoriteModel> _favoites = {};

  Map<int, FavoriteModel> get favoitesItem {
    return _favoites;
  }

And then you can fetch your data:

Future<void> getFavoriteList({
  @required int userId,
}) async {
  try {
    final response = await http.get("your url");
    final extractedData = json.decode(response.body);
    if (extractedData == null) {
      return;
    }
    final Map<int, YourModel> loadedProducts = {};

    print("Mahdi: favorite food ${extractedData['RIFUSD']}");

    final lastExtract = extractedData['RIFUSD'];

    lastExtract.forEach((prodData) {
      loadedProducts.putIfAbsent(
        prodData['timestamp'],
            () => YourModel(
          timestamp: prodData['timestamp'],
          open: prodData['open'],
        ),
      );
    });

    _favoites = loadedProducts;
    print("Mahdi ${_favoites.length}");
  } catch (error) {
    print("Mahdi E: $error");
    throw (error);
  }
}

I hope this works for you

data/raw_data_1.dart

const rawData = '''
{
   "RIFUSD":[
      {
   ....
      }
   ]
}
''';

main.dart

import 'dart:convert';

import 'data/raw_data_1.dart';


class NetService {
  static Future<Map<String, Object>> fetchData() {
    return Future.delayed(Duration(seconds: 2), () => rawData)
      .then((response) => jsonDecode(response));
  }
}

main(List<String> args) async {
  var data = await NetService.fetchData();
  var globalData = GlobalData.fromJson(data);
  print(globalData.data[0].id);
  print(globalData.data[0].candles[0].timestamp_UTC.toLocal().toString());
  print(globalData.data[0].candles[0].open.toString());
  print(globalData.data[0].candles[0].close.toString());
  print(globalData.data[0].candles[0].min.toString());
  print(globalData.data[0].candles[0].max.toString());
  print(globalData.data[0].candles[0].volume.toString());
  print(globalData.data[0].candles[0].volumeQuote.toString());
}

class Candle {
  DateTime timestamp_UTC;
  double open, close, min, max, volumeQuote;
  int volume;

  Candle.fromJson(Map<String, Object> jdata) {
    timestamp_UTC = DateTime.tryParse(jdata['timestamp']);
    open = double.tryParse(jdata['open']);
    close = double.tryParse(jdata['close']);
    min = double.tryParse(jdata['min']);
    max = double.tryParse(jdata['max']);
    volume = int.tryParse(jdata['volume']);
    volumeQuote = double.tryParse(jdata['volumeQuote']);
  }
}

class EntryOA {
  String id;
  List<Candle> candles;

  EntryOA.fromJson(MapEntry<String, Object> jdata) {
    this.id = jdata.key;
    var list = jdata.value as List<Object>;
    this.candles = List<Candle>.generate(list.length, (i) => Candle.fromJson(list[i] as Map<String, Object>));
  }
}

class GlobalData {
  List<EntryOA> data;
  
  GlobalData.fromJson(Map<String, Object> jdata) {
    data = jdata.entries.map((me) => EntryOA.fromJson(me)).toList();
  }
}

Result:

RIFUSD
2021-02-13 11:00:00.000
0.325737
0.325737
0.325737
0.325737
49
15.961113

You don't need to write dart file manually. You can use Online tool like Convert JSON response into Dart. I try it and the below is Dart class for your JSON response.

class Model_Candle {
  List<RIFUSD> rIFUSD;
  List<BERRYUSD> bERRYUSD;

  Model_Candle({this.rIFUSD, this.bERRYUSD});

  Model_Candle.fromJson(Map<String, dynamic> json) {
    if (json['RIFUSD'] != null) {
      rIFUSD = new List<RIFUSD>();
      json['RIFUSD'].forEach((v) {
        rIFUSD.add(new RIFUSD.fromJson(v));
      });
    }
    if (json['BERRYUSD'] != null) {
      bERRYUSD = new List<BERRYUSD>();
      json['BERRYUSD'].forEach((v) {
        bERRYUSD.add(new BERRYUSD.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    if (this.rIFUSD != null) {
      data['RIFUSD'] = this.rIFUSD.map((v) => v.toJson()).toList();
    }
    if (this.bERRYUSD != null) {
      data['BERRYUSD'] = this.bERRYUSD.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class RIFUSD {
  String timestamp;
  String open;
  String close;
  String min;
  String max;
  String volume;
  String volumeQuote;

  RIFUSD(
      {this.timestamp,
      this.open,
      this.close,
      this.min,
      this.max,
      this.volume,
      this.volumeQuote});

  RIFUSD.fromJson(Map<String, dynamic> json) {
    timestamp = json['timestamp'];
    open = json['open'];
    close = json['close'];
    min = json['min'];
    max = json['max'];
    volume = json['volume'];
    volumeQuote = json['volumeQuote'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['timestamp'] = this.timestamp;
    data['open'] = this.open;
    data['close'] = this.close;
    data['min'] = this.min;
    data['max'] = this.max;
    data['volume'] = this.volume;
    data['volumeQuote'] = this.volumeQuote;
    return data;
  }
}

Now to access the value of RIFUSD you can write code like below

 final Map<String, dynamic> parsed = await wrapper.get_CategoryFull(catid);
final model = get_model_category.fromJson(parsed);
if (model.RIFUSD.length > 0) {
      for (int i = 0; i < model.RIFUSD.length; i++) {
        print( "timespamt "+ model.RIFUSD[i].timestamp.tostring() );
      }

    }