AsyncVar #

AsyncVar is a simple and efficient solution for managing asynchronous operations in Flutter. It handles loading state, error state, and data state within a single variable, reducing boilerplate code and making your code more concise.

How to Use #

1. Add the AsyncVar class to your project.
2. Refactor your ViewModel to use AsyncVar:
   • Instead of manually managing loading, error, and data variables, use AsyncVar to handle these states automatically.

Example Usage #

Before AsyncVar: #

class EventListViewModel extends ChangeNotifier {
  final NetworkServiceProtocol service;

  EventListViewModel(this.service)
      : _hostedEventsLoading = false,
        _hostedEvents = [],
        _hostedEventsError = null {
    getHostedEvents();
  }

  bool _hostedEventsLoading;
  bool get hostedEventsLoading => _hostedEventsLoading;
  List<EventGet> _hostedEvents;
  List<EventGet> get hostedEvents => _hostedEvents;
  String? _hostedEventsError;
  String? get hostedEventsError => _hostedEventsError;

  Future<void> getHostedEvents() async {
    _hostedEventsLoading = true;
    _hostedEventsError = null;
    notifyListeners();

    try {
      _hostedEvents = await service.getHostedEvents();
    } catch (e) {
      _hostedEventsError = e.toString();
    }

    _hostedEventsLoading = false;
    notifyListeners();
  }
}

After Refactoring with AsyncVar: #

class EventListViewModel extends ChangeNotifier {
  final NetworkServiceProtocol service;

  late final AsyncVar<List<EventGet>> _hostedEvents;
  List<EventGet> get hostedEvents => _hostedEvents.data ?? [];

  EventListViewModel(this.service) {
    _hostedEvents = AsyncVar<List<EventGet>>(
      operation: () async => service.getHostedEvents(),
      parentNotifier: this,
    );
    _hostedEvents.doIt();
  }
}

Key Features of AsyncVar: #

• Automatically Manages State: Handles loading, error, and data states with a single variable.
• Reduces Boilerplate: No need to manually manage loading and error flags in your ViewModel.
• Reactive: Automatically notifies listeners of state changes.

Setup: #

1. Add AsyncVar to your project by copying the class definition.
2. Initialize AsyncVar in your ViewModel and call doIt() to perform the asynchronous operation.
3. Access the loading, error, and data properties directly from the AsyncVar instance in your ViewModel.

Methods: #

• doIt(): Starts the asynchronous operation and updates the state (loading, data, error).
• data: The result of the asynchronous operation.
• loading: Indicates whether the operation is still in progress.
• error: Holds the error message if the operation fails.

Conclusion #

AsyncVar simplifies asynchronous state management by consolidating loading, error, and data handling into a single variable, making your code cleaner and easier to maintain.

Additional information #

• Contributions: Contributions are welcome! Open an issue or submit a pull request.
• issues: If you encounter any issues, please feel free to reach out to Email: irshad365@flexxxlab.com