Reload UICollectionView header or footer?

Question

I have some data that is fetched in another thread that updates a UICollectionView\'s header. However, I\'ve not found an efficient way of reloading a supplementary view suc

Answer 1

Swift 3/4/5 version:

collectionView.collectionViewLayout.invalidateLayout()

Caution!

If you change the number of collectionView items at the same time (for example you show the footer only if all cells were loaded), it will crash. You need to reload the data first, to make sure that the number of items is the same before and after invalidateLayout():

collectionView.reloadData()
collectionView.collectionViewLayout.invalidateLayout()