cancelable_notify.dart

mixin CancelableNotify on ChangeNotifier {
  bool _mounted = true;

  @override
  void notifyListeners() {
    if (_mounted) super.notifyListeners();
  }

  @override
  void dispose() {
    _mounted = false;
    super.dispose();
  }
}

/// Usage:
/// class PageController extends ChangeNotifier with CancelableNotify {
///   PageController() {
///     initText();
///   }
///
///   String text = '';
///
///   void initText() async {
///     await Future.delayed(const Duration(milliseconds: 4000));
///     text = 'init';
///     notifyListeners();
///   }
/// }