How to set UICollectionViewCell Width and Height programmatically

Question

I am trying to implement a CollectionView. When I am using Autolayout, my cells won\'t change the size, but their alignment.

Now I would rather want to

Answer 1

If, like me, you need to keep your custom flow layout's itemSize dynamically updated based on your collection view's width, you should override your UICollectionViewFlowLayout's prepare() method. Here's a WWDC video demoing this technique.

class MyLayout: UICollectionViewFlowLayout {
    
    override func prepare() {
        super.prepare()
        
        guard let collectionView = collectionView else { return }
        
        itemSize = CGSize(width: ..., height: ...)
    }
    
}