How to access JSON nested data in flutter dart

Question

I have the below json data, wherein I want to access the values inside the feeling_percentage.

{
    "status": "200",
    "data": {
        "feeling_percentage": {
            "Happy": "0",
            "Sad": "0",
            "Energetic": "0",
            "Calm": "0",
            "Angry": "0",
            "Bored": "0"
        },
    }
}

I am able to fetch it using the below API code

Future<List<Data>> makePostRequest() async {
  List<Data> list = [];
  final uri = Uri.parse('<api>');
  final headers = {'Content-Type': 'application/json', 'X-Api-Key':'<api_key>'};
  Map<String, dynamic> body = {'user_id': 3206161992, 'feeling_date': '15-04-2022'};
  String jsonBody = json.encode(body);
  final encoding = Encoding.getByName('utf-8');

  Response response = await post(
    uri,
    headers: headers,
    body: jsonBody,
    encoding: encoding,
  );

  int statusCode = response.statusCode;
  String responseBody = response.body;
  print('response body'+ responseBody);
}

After reading few articles, still not able to figure out how do I access the percentage of happy, sad inside the feeling_percentage.
I have created the model as

class Data{
  FeelingPercentage feelingPercentage;

  Data(
      {required this.feelingPercentage});

  factory Data.fromJson(Map<String, dynamic> json) {
    return Data(
        feelingPercentage: FeelingPercentage.fromJson(json["data"]),
        );
  }
}

class FeelingPercentage {
  String? happy;
  String? sad;
  String? energetic;
  String? calm;
  String? angry;
  String? bored;

  FeelingPercentage({this.happy, this.sad, this.energetic, this.calm, this.angry, this.bored});

  factory FeelingPercentage.fromJson(Map<String, dynamic> json) {
    return FeelingPercentage(
      happy: json["happy"] as String,
      sad: json["sad"] as String,
      energetic: json["energetic"] as String,
      calm: json["calm"] as String,
      angry: json["angry"] as String,
      bored: json["bored"] as String,
    );
  }
}

Seems like you're not accessing the 'feeling_percentage' key at all. — Tomer Ariel
– Tomer Ariel, Commented May 27, 2022 at 12:57

mezoni · Accepted Answer · 2022-05-28 07:11:12Z

1

Another way:

import 'package:fast_json/fast_json_selector.dart' as parser;

void main() {
  final path = '{}.data.{}.feeling_percentage';
  final level = path.split('.').length;
  void select(parser.JsonSelectorEvent event) {
    final levels = event.levels;
    if (levels.length == level && levels.join('.') == path) {
      print(event.lastValue);
      event.lastValue = null;
    }
  }

  parser.parse(_source, select: select);
}

const _source = '''
{
    "status": "200",
    "data": {
        "feeling_percentage": {
            "Happy": "0",
            "Sad": "0",
            "Energetic": "0",
            "Calm": "0",
            "Angry": "0",
            "Bored": "0"
        }
    }
}''';

Output:

{Happy: 0, Sad: 0, Energetic: 0, Calm: 0, Angry: 0, Bored: 0}

answered May 28, 2022 at 7:11

mezoni

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Comments

Ali Bakhtiyari · Accepted Answer · 2022-05-27 13:09:01Z

1

You can use this website to convert your JSON object to a dart class. it automatically creates the fromJson function, which can be used to pass JSON and receive the Dart objects.

answered May 27, 2022 at 13:09

Ali Bakhtiyari

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Comments

Shahzad Umar Baig · Accepted Answer · 2022-05-27 13:06:29Z

0

Change this line in your model feelingPercentage: FeelingPercentage.fromJson(json["data"]), to feelingPercentage: FeelingPercentage.fromJson(json["data"]["feeling_percentage"]),

This will fix your issue.

answered May 27, 2022 at 13:06

Shahzad Umar Baig

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Comments

J. S. · Accepted Answer · 2022-05-27 13:15:59Z

0

You can do a JSON decode that will will result in a map, and then do the assigned like you are doing on your from Json factory, but as another constructor instead:

Class

Todo.fromMap(Map map) :
    this.title = map['title'],
    this.completed = map['completed'];

In use

Todo.fromMap(json.decode(item))

answered May 27, 2022 at 13:15

J. S.

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2 Comments

Lav Sharma Over a year ago

after using json.decode() i am getting error as Exception has occurred. _TypeError (type 'Null' is not a subtype of type 'String') but response.body() is printing the data

J. S. Over a year ago

It seems like one of the values you are getting from your json and trying to convert into your object may be null. You may have to review your data and do validations for nulls.

user18309290 · Accepted Answer · 2022-05-28 08:15:14Z

0

First decode response.body, then create FeelingPercentage object from json["data"]["feeling_percentage"] map.

Future<FeelingPercentage> makePostRequest() async {
...
  final json = json.decode(response.body);
  return FeelingPercentage.fromJson(json["data"]["feeling_percentage"])
}

class FeelingPercentage {
  String? happy;
  String? sad;
  String? energetic;
  String? calm;
  String? angry;
  String? bored;

  FeelingPercentage({this.happy, this.sad, this.energetic, this.calm, this.angry, this.bored});

  factory FeelingPercentage.fromJson(Map<String, dynamic> json) {
    return FeelingPercentage(
      happy: json["Happy"] as String,
      sad: json["Sad"] as String,
      energetic: json["Energetic"] as String,
      calm: json["Calm"] as String,
      angry: json["Angry"] as String,
      bored: json["Bored"] as String,
    );
  }
}

edited May 28, 2022 at 8:15

answered May 27, 2022 at 16:53

user18309290

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2 Comments

Lav Sharma Over a year ago

Error at happy: json["happy"] as String, as _CastError (type 'Null' is not a subtype of type 'String' in type cast)

user18309290 Over a year ago

JSON field names seem to have the first letter as capital: "Happy" instead of "happy".

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