How can a vertical list be incorporated into each horizontal cell on an orthogonal UICollectionView compositional layout using iOS nested scrolling?

edit

To incorporate a vertical list into each horizontal cell on an orthogonal UICollectionView compositional layout using iOS nested scrolling, follow these steps:

1. Create a custom UICollectionViewCell that will contain the vertical UICollectionView. You can let the cell conform to the UICollectionViewDelegate and UICollectionViewDataSource protocols, and add a vertical UICollectionView to it in the cell's init method.

2. Implement the necessary UICollectionViewDelegate and UICollectionViewDataSource methods for the vertical UICollectionView inside the custom UICollectionViewCell class.

3. Add the custom UICollectionViewCell to the UICollectionView compositional layout section that you want to contain the vertical list. You can do this by registering the custom cell class:

collectionView.register(MyCustomCollectionViewCell.self, forCellWithReuseIdentifier: "CustomCell")

1. In the UICollectionViewDelegate's cellForItemAt method, dequeue and configure the custom cell class and return it:

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CustomCell", for: indexPath) as! MyCustomCollectionViewCell

    // Configure the cell with the data for the vertical UICollectionView
    // ...

    return cell
}

1. Set the vertical UICollectionView's height to be the height of the parent horizontal UICollectionView, and set the UICollectionView compositional layout item height to be the height of the horizontal UICollectionView. This will ensure that each horizontal cell contains a vertical list that fills the entire cell.

let itemSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .absolute(collectionView.bounds.height))
let item = NSCollectionLayoutItem(layoutSize: itemSize)
item.contentInsets = NSDirectionalEdgeInsets(top: 0, leading: 10, bottom: 0, trailing: 10)

let groupSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .absolute(collectionView.bounds.height))
let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitems: [item])
group.contentInsets = NSDirectionalEdgeInsets(top: 10, leading: 0, bottom: 10, trailing: 0)

let section = NSCollectionLayoutSection(group: group)
section.orthogonalScrollingBehavior = .groupPaging

1. In the viewDidLoad method, enable the nested scrolling for both the horizontal and vertical UICollectionViews:

collectionView.isDirectionalLockEnabled = true // if needed
collectionView.alwaysBounceVertical = true
collectionView.alwaysBounceHorizontal = true
collectionView.isPagingEnabled = true // if using groupPaging orthogonalScrollingBehavior

for scrollView in collectionView.subviews {
    if let verticalScrollView = scrollView as? UICollectionView {
        verticalScrollView.alwaysBounceHorizontal = false
    }
}

These steps should result in a horizontal UICollectionView layout with a vertical list inside each cell that scrolls both horizontally and vertically.