Tell you what UICollectionView is.
UICollectionView – allows you to arrange your images, photos in the selected order, in a column or row.
@IBOutlet weak var collectionView: UICollectionView!
When loading the CollectionView, you must specify the data for all cells. To create it, you need to use three protocols: UICollectionViewDataSource, UICollectionViewDelegate, and UICollectionViewDelegateFlowLayout.
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