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 }

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 }