Flutter Json Encode List

Question

How to encode list to json?

This is my class for Json.

class Players{
  List<Player> players;

  Players({this.players});

  factory Players.fromJson(List<dynamic> parsedJson){

    List<Player> players = List<Player>();
    players = parsedJson.map((i)=>Player.fromJson(i)).toList();

    return Players(
      players: players,
    );
  }
}

class Player{
  final String name;
  final String imagePath;
  final int totalGames;
  final int points;

  Player({this.name,this.imagePath, this.totalGames, this.points});

  factory Player.fromJson(Map<String, dynamic> json){

    return Player(
      name: json['name'],
      imagePath: json['imagePath'],
      totalGames: json['totalGames'],
      points: json['points'],
    );
  }
}

I managed to decode with fromJson, the result is in List. Now that I have another player to add in json and want to encode the list to json, have no idea to do it. It result always failed.

var json = jsonDecode(data);
List<Player> players = Players.fromJson(json).players;
Player newPlayer = Player(name: _textEditing.text,imagePath: _imagePath,totalGames: 0,points: 0);
players.add(newPlayer);
String encode = jsonEncode(players.players);

What do I need to add on Players or Player?

Your code is incorrect. The `players` variable is of type `List`. Accordingly, this code `players.players` will not work, because `List` does not have a `players` field. — mezoni, Jun 05 '19 at 08:46

score 36 · Accepted Answer · edited Jun 10 '20 at 19:08

36

Add toJson method to your Player class:

Map<String, dynamic> toJson(){
  return {
    "name": this.name,
    "imagePath": this.imagePath,
    "totalGames": this.totalGames,
    "points": this.points
  };
}

Then you can call jsonEncode on the list of players:

String encoded = jsonEncode(players) // this will automatically call toJson on each player

edited Jun 10 '20 at 19:08

Sami Haddad

1,356
10
15

answered Mar 06 '19 at 14:08

Sami Kanafani

14,244
6
45
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9

You don't need the static function. `jsonEncode` will work with a `List` if the class has `toJson` implemented. – Lucas Mar 06 '19 at 19:30
@Lucas You are right! No need for static function. Thank you! – willy wijaya Mar 07 '19 at 03:06

Lucio Pelinson · Answer 2 · 2020-02-05T18:34:27.820

17

Add on class:

Map<String,dynamic> toJson(){
    return {
        "name": this.name,
        "imagePath": this.imagePath,
        "totalGames": this.totalGames,
        "points": this.points
    };
  }

and call

String json = jsonEncode(players.map((i) => i.toJson()).toList()).toString();

edited Feb 05 '20 at 18:34

answered Feb 05 '20 at 16:15

Lucio Pelinson

430
5
7

1

Can you explain why is variable json declared as String? I'm quite confused – Steven Apr 30 '20 at 05:27
1

Hi Steven, sometimes we need to work with json as plain/text, but it's just an example. – Lucio Pelinson May 06 '20 at 04:12
This was so helpful. Thank you. – MUHINDO Jun 10 '23 at 09:11

score 7 · Answer 3 · answered Oct 01 '19 at 15:37

7

List jsonList = players.map((player) => player.toJson()).toList();
print("jsonList: ${jsonList}");

answered Oct 01 '19 at 15:37

FreddCha

465
2
8
15

4

Can you please add description on why this solves the issue mentioned in the question ? – Manoj Choudhari Oct 01 '19 at 15:56

Flutter Json Encode List

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