Model a server response with Class-CodePudding

I have a flutter application, which uses some server APIs.

When there is a successful response from the server, it would return json back:

{"success": true, "message": "success", "data": {"id": "21EE"} }

However, when there is failure, it would return:

{"success": false, "message": "failure"}

For more strict-typed use of flutter, I try to model the response.

Here is my try:

class ServerResponse {
  final bool success;
  final String message;

  ServerResponse({
    required this.success,
    required this.message,
  });
}



class _AuthAutenticationData {
  final String id;

  _AuthAutenticationData({
    required this.id,
  });
}

class AutoAuthenticateResponse extends ServerResponse {
  final _AuthAutenticationData? data;

  AutoAuthenticateResponse({
    required success,
    required message,
    this.data,
  }) : super(success: success, message: message);
}

Now, I have a function which calls a specific API:

Future<void> autoAuth() async {
  final url = Uri.parse('${this._baseURL.toString()}/auto-auth');

  try {
    final response = await http.post(url, headers: {
      'Authorization': 'SXXX',
    });
    print(response.body);
    final AutoAuthenticateResponse responseBody = json.decode(response.body);

    if (responseBody.success) {
      return setUser(new User(id: responseBody.data!.id));
    }

    setUser(null);
  } catch (error) {
    print(error);
    setUser(null);
  }
}

Some code is irrelevant, but bottom line is that I receive the following error in the line: final AutoAuthenticateResponse responseBody = json.decode(response.body);:

I/flutter (14139): type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'AutoAuthenticateResponse'

I guess my solution is bad. Any advice how to fix it?

CodePudding user response：

Use this link to generate models for your response

CodePudding user response：

Well, you can use nullsafety feature for this. Since it's only if when the failure the data is not being returned.

{"success": true, "message": "success", "data": {"id": "21EE"} }

you can use this : https://meruya-techhnology.github.io/json-to-dart/

Then the result will be a 2 class

class YourClass {
  final bool success;
  final String message;
  final Data? data;

  YourClass({this.success, this.message, this.data});

  factory YourClass.fromJson(Map<String, dynamic> json) => YourClass(
    success : json['success'],
    message : json['message'],
    data : json['data'] != null ? new Data.fromJson(json['data']) : null;
  );

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['success'] = this.success;
    data['message'] = this.message;
    if (this.data != null) {
      data['data'] = this.data.toJson();
    }
    return data;
  }
}

And

class Data {
  String id;

  Data({this.id});

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

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    return data;
  }
}

Then you can use it like this :

Future<void> autoAuth() async {
  final url = Uri.parse('${this._baseURL.toString()}/auto-auth');

  try {
    final response = await http.post(url, headers: {
      'Authorization': 'SXXX',
    });
    debugPrint(response.body);
    final responseBody = YourClass.fromJson(response.body)
    if (responseBody.success) {
      return setUser(new User(id: responseBody.data!.id));
    }
    setUser(null);
  } catch (error) {
    print(error);
    setUser(null);
  }
}

another advice is use debugPrint instead of print, here you can read more : https://medium.com/flutter-community/debugprint-and-the-power-of-hiding-and-customizing-your-logs-in-dart-86881df05929