Parsing json array response / flutter

Question

Did this according to this manual https://www.bezkoder.com/dart-flutter-parse-json-string-array-to-object-list/ Dart/Flutter parse array of JSON objects into List

JSON that comes from the server

{"myChannels":[{"id":"2","name":"channel2test","imageUrl":"image1.png"},{"id":"2","name":"channel2test","imageUrl":"image2.png"}]}

Model Class

class ChannelModel {
  String channelID;
  String channelName;
  String imageUrl;
  ChannelModel(this.channelID, this.channelName, this.imageUrl);

  factory ChannelModel.parsingChannels(dynamic json) {
    return ChannelModel(json['channelID'] as String,
        json['channelName'] as String, json['imageUrl'] as String);
  }
  @override
  String toString() {
    return '{ ${this.channelID}, ${this.channelName}, ${this.imageUrl} }';
  }
}

Main block

    try {
      final response = await http.post(
        url,
        body: json.encode({
          'action': 'getMyChannels',
          'userID': userID,
          'returnSecureToken': true,
        }),
      );
      //  print(jsonDecode(response.body));

      var extractedData =
          jsonDecode(response.body)['myChannels'] as List<dynamic>;
      List<ChannelModel> channelObjects = extractedData
          .map((cJson) => ChannelModel.parsingChannels(cJson))
          .toList();

      print(channelObjects);
   
      channelObjects.forEach((Data) {
        print('test');           
      });

the results is the following...

print(channelObjects) > outputs > []
print('test') > not working , channelObjects not looping

esentis · Accepted Answer · 2021-09-18 21:39:12Z

2

I would suggest serializing your response to dart classes. It would be much easier to access the data you want.

class ApiResponse {
  ApiResponse({
    required this.myChannels,
  });

  List<MyChannel> myChannels;

  factory ApiResponse.fromJson(Map<String, dynamic> json) => ApiResponse(
        myChannels: List<MyChannel>.from(
          json["myChannels"].map((x) => MyChannel.fromJson(x)),
        ),
      );
}

class MyChannel {
  MyChannel({
    required this.id,
    required this.name,
    required this.imageUrl,
  });

  String id;
  String name;
  String imageUrl;

  factory MyChannel.fromJson(Map<String, dynamic> json) => MyChannel(
        id: json["id"],
        name: json["name"],
        imageUrl: json["imageUrl"],
      );
}

Then you can use it this way :

final extractedData = ApiResponse.fromJson(json.decode(response.body) as Map<String, dynamic>);

And access the data you want

extractedData.myChannels[0].id
extractedData.myChannels[0].name
extractedData.myChannels[0].imageUrl

for (var ch in extractedData.myChannels){
 print(ch.id);
 print(ch.name);
 print(ch.imageUrl);
}

answered Sep 18, 2021 at 21:39

esentis

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1 Comment

David Over a year ago

I like your approach, but I could not fix my problem with it, don't know why, then I spent a bit more time , found an article with example and updated my code according to that article. But again it does not work, can you check my code please and say what you think ?

Temirlan Almassov · Accepted Answer · 2021-09-18 21:38:42Z

part 'example.g.dart';

@JsonSerializable()
class Channel{
  final String id;
  final String name;
  final String? imageUrl;
  Channel({required this.id, required this.name, this.imageUrl});
  factory Channel.fromJson(Map<String, dynamic> json) => _$ChannelFromJson(json);
  Map<String, dynamic> toJson() => _$ChannelToJson(this);
}



@JsonSerializable()
class ChannelList{
  final List<Channel> myChannels;
  ChannelList({required this.myChannels});
  factory ChannelList.fromJson(Map<String, dynamic> json) => _$ChannelListFromJson(json);
  Map<String, dynamic> toJson() => _$ChannelListToJson(this);
}

final extractedData = ChannelList.fromJson(json.decode(response.body));

https://pub.dev/packages/json_serializable

Using JsonSerializable more useful and understandable. You can read documentation of that package

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