Where to highlight UICollectionViewCell: delegate or cell?

Question

According to the Collection View Programming Guide one should handle the visual state of the cell highlights in the UICollectionViewDelegate. Like this:

Answer 1

It is enough for highlighting cell (Swift 4)

class MyCollectionViewCell: UICollectionViewCell {
...
    override var isHighlighted: Bool {
        didSet {
            if isHighlighted {
                self.contentView.alpha = 0.6
            }
            else {
                self.contentView.alpha = 1.0
            }
        }
    }
}