Why is it the passed data returns null in Flutter? I use Cloud Firestore as my data storage-CodePudding

I have a file named todo_repository.dart and has readTodo() function. Whenever I print the data variable here, there are returned contents/values but after I passed the data to another file named todo_list_cubit.dart, the data returns null value.

Here is the readTodo() of todo_repository.dart

  Future<dynamic> readTodo() async {
    try {
      final User user = auth.currentUser!;
      final uid = user.uid;

      await usersTodo.doc(uid).get().then((DocumentSnapshot documentSnapshot) {
        if (documentSnapshot.exists) {
          var data = documentSnapshot.data() as Map;
          //The data here is not empty
          print(data);
          return data;
        }
      });
    } on FirebaseException catch (e) {
      throw CustomError(
        code: e.code,
        message: e.message!,
        plugin: e.plugin,
      );
    } catch (e) {
      throw CustomError(
        code: 'Exception',
        message: e.toString(),
        plugin: 'flutter_error/server_error',
      );
    }
  }

Here is the readTodo() of todo_list_cubit.dart

Future<void> readTodo() async {
    try {
      emit(state.copyWith(
        todoListStatus: TodoListStatus.loading,
      ));

      //Start - Part of code where I have issue
      Map todoRepoRead = await todoRepository.readTodo();
      **after I passed the data from todoRepository.readTodo(), the value returns null**
      print(todoRepoRead);
      //End - Part of code where I have issue

      final rTodos = state.todos.map((Todo todo) {
        return Todo(
          id: todoRepoRead['id'],
          description: todoRepoRead['description'],
          completed: todoRepoRead['completed'],
        );
      }).toList();
      emit(state.copyWith(
        todoListStatus: TodoListStatus.loaded,
        todos: rTodos,
      ));
    } on CustomError catch (e) {
      emit(state.copyWith(
        todoListStatus: TodoListStatus.error,
        error: e,
      ));
    }
  }

CodePudding user response：

You should either use async/await or then, but not both.

Using just await, your code becomes:

Future<dynamic> readTodo() async {
  try {
    final User user = auth.currentUser!;
    final uid = user.uid;

    DocumentSnapshot documentSnapshot = await usersTodo.doc(uid).get();
    if (documentSnapshot.exists) {
      var data = documentSnapshot.data() as Map;
      //The data here is not empty
      print(data);
      return data;
    };
    // TODO: you still need to return something here
  } on FirebaseException catch (e) {
    throw CustomError(
      code: e.code,
      message: e.message!,
      plugin: e.plugin,
    );
  } catch (e) {
    throw CustomError(
      code: 'Exception',
      message: e.toString(),
      plugin: 'flutter_error/server_error',
    );
  }
}