How to change collection view scroll direction?

This is how you create it in code with UICollectionViewFlowLayout

let layout = UICollectionViewFlowLayout()
layout.scrollDirection = .vertical
let collectionView = UICollectionView(frame: frame, collectionViewLayout: layout)

This is how if you are working with an existent collection view

if let layout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout {
    layout.scrollDirection = .vertical
}

Thanks for reading :)