api_response.dart

class ApiResponse<T> {
  Status status;
  T data;
  String message;
  
ApiResponse.loading(this.message) : status = Status.LOADING;
ApiResponse.completed(this.data) : status = Status.COMPLETED;
ApiResponse.error(this.message) : status = Status.ERROR;
  
@override
  String toString() {
    return "Status : $status \n Message : $message \n Data : $data";
  }
}

enum Status { LOADING, COMPLETED, ERROR }

Hello, I would like to ask you the meaning of the lines 6-8. Are they a particular type of method in Dart? Thank you a lot!

Hey @Devizz998, they are just factory / named constructors. You can read more about them here ->
https://dart.dev/guides/language/language-tour#named-constructors

this ->

ApiResponse.loading(this.message) : status = Status.LOADING;

is similiar to

ApiResponse.loading(this.message) {
     status = Status.LOADING;
}

Thank you so much, I forgot about the short notation with : .
Congratulation for your tutorial!

Getting this error

With null safety, it will be something like that:

class ApiResponse<T> {
  Status status = Status.LOADING;
  T? data;
  String message = '';

  ApiResponse.loading(this.message) : status = Status.LOADING;
  ApiResponse.completed(this.data) : status = Status.COMPLETED;
  ApiResponse.error(this.message) : status = Status.ERROR;

  @override
  String toString() {
    return "Status : $status \n Message : $message \n Data : $data";
  }
}

enum Status { LOADING, COMPLETED, ERROR }