Flutter - unable to parse json array

Question

I want to fetch list of cities from rest webservice, this way:

Future<List<City>> fetchCities() async {
  final response =
  await http.get('https://my-url/city',
  headers: {HttpHeaders.acceptHeader: "application/json"});

  if (response.statusCode == 200) {
    // If the call to the server was successful, parse the JSON
    return compute(parseCities, response.body);
  } else {
    // If that call was not successful, throw an error.
    throw Exception('Failed to load cities');
  }
}

Then to parse:

List<City> parseCities(String responseBody) {
  final parsed = json.decode(responseBody)['data']['children'].cast<Map<String, dynamic>>();

  return parsed.map<City>((json) => City.fromJson(json['data'])).toList();
}

And this is City class definition:

class City {
  final String id;
  final String name;

  City({this.id, this.name});

  factory City.fromJson(Map<String, dynamic> json) {
    return City(
      id: json['id'],
      name: json['name'],
    );
  }
}

My example responseBody is:

[{\"id\":\"599\",\"name\":\"Bia\u0142ystok-dev\",\"location\":{\"long\":\"23.15\",\"lat\":\"53.13\"}}]

(for now, I want to ommit location and only fetch id and name). My json.decode throws exception:

type 'String' is not a subtype of type 'int' of 'index'

How to fix that? Any ideas?

Jordan Davies · Accepted Answer · 2019-02-04 12:31:31Z

2

The json string you have posted does not contain the keys data or children so to parse that json you would need to change your parse method to the following:

List<City> parseCities(String responseBody) {
  final parsed = json.decode(responseBody).cast<Map<String, dynamic>>();

  return parsed.map<City>((json) => City.fromJson(json)).toList();
}

although I think its good practice to use List.from instead of .cast

final parsed = List<Map<String, dynamic>>.from(json.decode(responseBody));

edited Feb 4, 2019 at 12:31

answered Feb 4, 2019 at 12:22

Jordan Davies

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