SectionIndexTitles for a UICollectionView

Question

So I implemented a proper TableView with a search functionality and sectionIndexTitles. Now, I am trying to implement a UICollectionView

Answer 1

You can provide this header by implementing and returning a value for the following function for UICollectionViewDataSource

collectionView:viewForSupplementaryElementOfKind:atIndexPath:

Note that the size of the header will be from the height value of the CGRect returned from UICollectionViewFlowLayoutDelegate method collectionView:layout:referenceSizeForHeaderInSection: