listenWithPrevious<T> method

void listenWithPrevious<T>(Pod<T> pod, void listener(T? previous, T next))

Listen a pod with previous value

Implementation

void listenWithPrevious<T>(
  Pod<T> pod,
  void Function(T? previous, T next) listener,
) {
  final container = PodScope.of(this)..get<T>(pod);

  _listeners.putIfAbsent('$_listenWithPrevious${pod.hashCode}$hashCode', () {
    final callbackWrapper = _CallbackWrapper<T>();

    final cancelPodSubscribe =
        container.subscribeWithPrevious<T>(pod, (previous, next) {
      listener(previous, next);
    });

    final modalRoute = ModalRoute.of(this);

    if (modalRoute != null) {
      Future<bool> willPopCallback() {
        WidgetsBinding.instance.addPostFrameCallback((_) {
          cancelPodSubscribe();
          modalRoute
              .removeScopedWillPopCallback(callbackWrapper.willPopCallback!);

          _listeners.remove('$_listenWithPrevious${pod.hashCode}$hashCode');
        });

        return Future.value(true);
      }

      callbackWrapper.willPopCallback = willPopCallback;
      modalRoute.addScopedWillPopCallback(callbackWrapper.willPopCallback!);
    }
    return null;
  });
}