UpdateCollectionviewDelegates.swift

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

    if collectionView == baseCollectionView {
        ///We have 2 collectionviews, so we must differentiate.
        cell.backgroundColor = .green
        cell.nameLabel.text = newBaseCollectionViewArray[indexPath.item].labelName
    } else {
        cell.backgroundColor = .red
        cell.nameLabel.text = secondCollectionViewArray[indexPath.item].labelName
    }
    return cell
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    if collectionView == baseCollectionView {
        ///If this collectionview is the second one
        return newBaseCollectionViewArray.count
    } else { ///If not, this must be the first collection view.
        return secondCollectionViewArray.count
    }
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    if collectionView == baseCollectionView {
        let alphabetLetter = newBaseCollectionViewArray[indexPath.item]
        secondCollectionViewArray.append(alphabetLetter)
        let newIndexPath = IndexPath(item: secondCollectionViewArray.count - 1, section: 0)
        secondCollectionView.insertItems(at: [newIndexPath])

        newBaseCollectionViewArray.remove(at: indexPath.item)
        baseCollectionView.deleteItems(at: [indexPath])

    } else {
        let alphabetLetter = secondCollectionViewArray[indexPath.item]
        newBaseCollectionViewArray.insert(alphabetLetter, at: 0)
        let newIndexPath = IndexPath(item: 0, section: 0)
        ///I guess we'll put it at the front for now?
        baseCollectionView.insertItems(at: [newIndexPath])

        secondCollectionViewArray.remove(at: indexPath.item)
        secondCollectionView.deleteItems(at: [indexPath])
    }
}