Parsing Json in flutter

Question

I am learning flutter and trying to parse a json which is array or json objects like this.

[
  {
    "albumId": 1,
    "id": 1,
    "title": "accusamus beatae ad facilis cum similique qui sunt",
    "url": "https://via.placeholder.com/600/92c952",
    "thumbnailUrl": "https://via.placeholder.com/150/92c952"
  },
  {
    "albumId": 1,
    "id": 2,
    "title": "reprehenderit est deserunt velit ipsam",
    "url": "https://via.placeholder.com/600/771796",
    "thumbnailUrl": "https://via.placeholder.com/150/771796"
  },]

And here is my fetch function which fetches this data from server.

 fetch() async{

   var client = new http.Client();
  try {
  var uriResponse = await 
  client.get('https://jsonplaceholder.typicode.com/photos');
  if(uriResponse.statusCode == 200){

  var data = json.decode(uriResponse.body);//data is array of objects
  List<Photo> pics= data.map((Map<String,dynamic> model)=> Photo.fromJson(model)).toList();
  setState(() {
    photos = data;
    _isLoading = false;
  });
}
  } finally {
client.close();
  }
}

But the line ;

List<Photo> pics= data.map((Map<String,dynamic> model)=> Photo.fromJson(model)).toList();

gives me error that:

ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: type '(Map<String, dynamic>, dynamic) => Photo' is not a subtype of type '(dynamic) => dynamic' of 'f'

Here is my Photo PODO class.

  class Photo {
  final int id;
  final String title;
  final String url;
  final String thumbnailUrl;

  Photo({this.id, this.title,this.url, this.thumbnailUrl});

  factory Photo.fromJson(Map<String, dynamic> json) {
    return Photo(
      id: json['id'] as int,
      title: json['title'] as String,
      thumbnailUrl: json['thumbnailUrl'] as String,
      url: json['url'] as String,
    );
  }
}

What i am doing wrong in the above code? Thanx in advance !

The best way use online json to dart pojo stackoverflow.com/questions/51901760/… — Amit Prajapati
– Amit Prajapati, Commented Oct 17, 2019 at 8:22

Lukas Kirner · Accepted Answer · 2019-04-10 08:32:04Z

2

You can use quicktype it lets you copy in your JSON string and generates the Dart Objects

answered Apr 10, 2019 at 8:32

Lukas Kirner

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Preeth Prathapan · Accepted Answer · 2019-07-11 10:44:01Z

1

In my project I have done like this and its working

pics = (data as List).map((model) => Photo.fromJson(model)).toList();

answered Jul 11, 2019 at 10:44

Preeth Prathapan

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Comments

Mangaldeep Singh Pannu · Accepted Answer · 2019-04-10 06:56:55Z

0

Try using

pics = data.map((i)=>Photo.fromJson(i)).toList();

You are receiving an json array and not json object from server

answered Apr 10, 2019 at 6:56

Mangaldeep Singh Pannu

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2 Comments

Vipin Dubey Over a year ago

this gives error : : [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: type 'List<dynamic>' is not a subtype of type 'List<Photo>'

Vipin Dubey Over a year ago

and when i changes it to dynamic then i cant access the Photo class variable

youssef ali · Accepted Answer · 2019-04-10 07:27:27Z

0

try this if it didnt work make sure to print the the response body

Iterable<dynamic> l = json.decode(uriResponse.body);
List<Post> posts = l.map((model) => Post.fromJson(model)).toList();

answered Apr 10, 2019 at 7:27

youssef ali

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