Determine if a provider has a value

[scopendo]

Hi – my app has a provider that contains a list of bookings. I also have a booking notifier that allows operations on a single booking. When initialising the booking notifier, I want to use the value from the list of bookings if it's in there, whilst loading the data for the booking asynchronously. This allows the UI to show something more quickly and then to update if the data was stale.

class BookingNotifier extends AutoDisposeFamilyAsyncNotifier<BookingInfo, int> {
  @override
  Future<BookingInfo> build(int arg) async {
    // See if we can find the booking in the list of current bookings
    final bookings = await ref.watch(Pods.currentBookings.future);
    final bi = bookings.firstWhereOrNull((bi) => bi.booking.id == arg);

    if (bi == null) {
      // We'll need to wait for the data to load
      return _loadBooking(arg);
    } else {
      // We can use the data we've got in the booking object whilst we wait
      // for the async data load to complete
      _loadBooking(arg)
          .then((bookingInfo) => state = AsyncData(bookingInfo))
          .withoutAwait();
      return bi;
    }
  }
  ...
}

This works fine, however, it will force provider Pods.currentBookings to load if it hasn't loaded already.

Is there a way to check whether a provider is already loaded without triggering a load?

[rrousselGit]

Are you looking for ref.exist(provider)?

[scopendo]

Yes – I was looking for something like that but was clearly looking in the place. Thanks @rrousselGit.