Invalid update: invalid number of items on UICollectionView

Question

I am stumped on this. Here is my scenario. In my Appdelegate, I am creating

1. An instance of a view controller that will be presented modally to collect two pi

Answer 1

In my case, numberOfItemsInSection was being called twice from self.performBatchUpdates (once for the BEFORE number, once for the AFTER number) because I was trying to insert something into the collectionView before the view controller had finished loading.

The solution is to add guard isViewLoaded else { return } before calling self.performBatchUpdates.