State Management

Provider Pattern

All ViewModels extend ChangeNotifier. They are registered as Factory or LazySingleton in service_locator.dart and consumed via context.watch<T>() or context.read<T>().

ViewModel Registry

// service_locator.dart
getIt.registerFactory<AuthViewModel>(() => AuthViewModel(getIt()));
getIt.registerFactory<HomeViewModel>(() => HomeViewModel(getIt(), getIt()));
getIt.registerFactoryParam<TripDetailViewModel, String, void>(
  (tripId, _) => TripDetailViewModel(getIt(), tripId),
);
getIt.registerFactoryParam<StudentsViewModel, String, void>(
  (tripId, _) => StudentsViewModel(getIt(), tripId),
);
getIt.registerFactory<IncidentsViewModel>(() => IncidentsViewModel(getIt()));
getIt.registerFactory<ProfileViewModel>(() => ProfileViewModel(getIt()));

HomeViewModel

Manages assigned bus, day trips, current location, and trip state.

class HomeViewModel extends ChangeNotifier {
  final HomeRepo _homeRepo;
  final LocationService _locationService;

  List<DayTripsModel> _dayTrips = [];
  BusModel? _assignedBus;
  LatLng? _currentLocation;
  bool _isLoading = false;

  List<DayTripsModel> get dayTrips => _dayTrips;
  BusModel? get assignedBus => _assignedBus;
  LatLng? get currentLocation => _currentLocation;

  Future<void> init() async {
    _isLoading = true;
    notifyListeners();

    await Future.wait([
      _loadBusAssignment(),
      _loadTrips(),
      _startLocationUpdates(),
    ]);

    _isLoading = false;
    notifyListeners();
  }

  Future<void> _loadBusAssignment() async {
    final result = await _homeRepo.getAssignedBus();
    result.fold(
      (failure) => null,
      (bus) => _assignedBus = bus,
    );
  }

  Future<void> _loadTrips() async {
    final result = await _homeRepo.getTrips();
    result.fold(
      (failure) => null,
      (trips) => _dayTrips = trips,
    );
  }

  Future<void> _startLocationUpdates() async {
    _locationService.locationStream.listen((position) {
      _currentLocation = LatLng(position.latitude, position.longitude);
      notifyListeners();
    });
  }
}

LocationService

Uses geolocator for GPS and buffers updates for batch sending:

class LocationService {
  Stream<Position> get locationStream {
    return Geolocator.getPositionStream(
      locationSettings: const LocationSettings(
        accuracy: LocationAccuracy.high,
        distanceFilter: 10, // meters
      ),
    );
  }

  Future<Position?> getCurrentPosition() {
    return Geolocator.getCurrentPosition();
  }
}