Reused cells in a UICollectionView show multiple UIImageViews when they should only show one

Question

Im having a problem with my UICollectionView. Initially it displays fine, showing a grid of cells, each cell with a single UIImageView. These

Answer 1

For anyone who is adding UICollectionView programmatically and have a custom cell, in other words no XIB file, then you have to add this line to viewDidLoad

[_collectionView registerClass:[CustomCell class] forCellWithReuseIdentifier:@"cellIdentifier"];