I want to serialize optionally JSON data from API as a list or as an object. Here I'm kinda recreating how DjangoRestFramework serializer works in Flutter. Where you can optionally past a parameter many=True or many=False to indicate there will be a lot of data (like a list) or there will be only one piece of data (like an object). Here is what it looks like in Django

serializer = BookSerializer(queryset, many=True)

My serializer in flutter currently only can serialize JSON data lists, but doesn't have the ability to serialize a JSON data object optionally. Examples of data will be:

// Data as a list
{
    "message": "Berhasil mengambil profile User",
    "statusCode": 200,
    "data": [
        {
            "id": 1,
            "avatar": "32412"
        }
        .
        .
        .
        .
        {
            "id": 1,
            "avatar": "32412"
        }
    ]
}

// Data as an object
{
    "message": "Berhasil mengambil profile User",
    "statusCode": 200,
    "data": {
        "id": 1,
        "avatar": "32412"
    }
}

This is my current code:

class Data {
  final int? id;
  final String? avatar;

  Data({
    required this.id,
    required this.avatar,
  });

  factory Data.fromJson(Map<String, dynamic> json) {
    final id = json['id'];
    final avatar = json['avatar'];

    return Data(
      id: id,
      avatar: avatar,
    );
  }
}

class UserProfileSeralizer {
  final String? message;
  final int? statusCode;
  final dynamic data;
  bool many = true;

  UserProfileSeralizer(this.many, {this.message, this.statusCode, this.data});

  factory UserProfileSeralizer.fromJson(Map<String, dynamic> json) {
    final message = json['message'];
    final statusCode = json['statusCode'];

    final tempDataJson = json['data'];
    // Assign data as List or as Data based on many's value
    if (many) {
      final List data = List.from(tempDataJson);
    } else {
      final Data data = Data.fromJson(tempDataJson);
    }

    return UserProfileSeralizer(
      message: message,
      statusCode: statusCode,
      data: data,
    );
  }
}

I thought I can just access the variable many in the factory and assign data variable based on the value of many. So I'm kinda lost here and need help.

Best regards.

CodePudding user response：

Try this:

class Data {
  final int? id;
  final String? avatar;

  Data({
    required this.id,
    required this.avatar,
  });

  factory Data.fromJson(Map<String, dynamic> json) {
    if(json.containsKey('id') && json.containsKey('avatar')) {}
    return Data(
      id: json['id'],
      avatar: json['avatar'],
    );
  }
}

class UserProfileSeralizer {
  final String? message;
  final int? statusCode;
  final dynamic data;

  UserProfileSeralizer({this.message, this.statusCode, this.data});

  factory UserProfileSeralizer.fromJson(Map<String, dynamic> json) {
    if(json['data'] is List) {
      return UserProfileSeralizer(
          message: json['message'], 
          statusCode: json['statusCode'], 
          data: json['data'].map((e) => Data.fromJson(e)).toList()
      );
    } else {
      return UserProfileSeralizer(
          message: json['message'], 
          statusCode: json['statusCode'], 
          data: Data.fromJson(json['data'])
      );
    }
  }
}

Note that I removed the boolean variable many because you were using it to check whether json[data] is a list or not, which is simpler if you cut to the chase.