Flutter State Management Matrix: ValueNotifier vs Bloc vs Riverpod vs GetX

class CartNotifier extends ValueNotifier<CartState> {
  CartNotifier() : super(const CartState(items: []));

  void updateQuantity(String id, int qty, int maxStock) {
    final clamped = qty.clamp(0, maxStock);
    final updated = value.items.map((it) => it.id == id ? it.copyWith(quantity: clamped) : it).toList();
    value = value.copyWith(items: updated);
  }
}

// In Widget Tree:
ValueListenableBuilder<CartState>(
  valueListenable: cartNotifier,
  builder: (context, state, _) => Text('Total: ${state.totalFormatted}'),
)

class CartCubit extends Cubit<CartState> {
  CartCubit() : super(const CartState.initial());

  void updateQuantity(String id, int qty, int maxStock) {
    final clamped = qty.clamp(0, maxStock);
    emit(state.copyWithQuantity(id, clamped));
  }
}

// In Widget Tree:
BlocBuilder<CartCubit, CartState>(
  buildWhen: (prev, curr) => prev.totalPrice != curr.totalPrice,
  builder: (context, state) => Text('Total: ${state.totalFormatted}'),
)

@riverpod
class CartEngine extends _$CartEngine {
  @override
  CartState build() => const CartState(items: []);

  void updateQuantity(String id, int qty, int maxStock) {
    state = state.withUpdatedQuantity(id, qty.clamp(0, maxStock));
  }
}

// In Widget Tree (ConsumerWidget):
Widget build(BuildContext context, WidgetRef ref) {
  final cart = ref.watch(cartEngineProvider);
  return Text('Total: ${cart.totalFormatted}');
}