UICollectionViewCell changes cell contents when scrolling - swift

Question

I have a custom UICollectionView. I am using a UIView instead of a UICollectionViewCell as I'm wanting to use the UIView elsewhere.
The UICollectionView scrolls only horizontally and has 14 cells; each with the UIView as its contents.
Inside this UIView is another UICollectionView which houses a UICollectionViewCell which is just an image of a dice.
So:
Outer UICollectionView with Cell
The cell has a UIView
The UIView has a UICollectionView and UICollectionViewCell
The UICollectionViewCell is just an imageView of a dice.
The problem I'm having is, when the UICollectionView scrolls horizontally, the contents of the cell are changing when they should remain static; sometimes it randomly moves the contents, or completely removes the contents.
I'm not sure what is causing this to happen.
How can I ensure that upon scrolling that the UICollectionView keeps its contents intact?
Outer UICollectionView:
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return allLocos?.count ?? 0
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell:OuterCollectionViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: "OuterCollectionViewCell", for: indexPath) as! OuterCollectionViewCell
if cell.cardView == nil {
let arr = UINib(nibName: "CardView", bundle: nil).instantiate(withOwner: nil, options: nil)
let view = arr[0] as! CardView
cell.contentView.addSubview(view)
cell.cardView = view
}
if let locos = self.allLocos {
let loco:EYLocomotive = locos[indexPath.row]
print(indexPath.row, loco.name, loco.orders)
cell.engineCardView?.setup(loco:loco)
}
cell.layoutIfNeeded()
return cell
}
I think the issue is being caused by this line:
cell.engineCardView?.setup(loco:loco)
My UIView (The cardView) has this code:
#IBOutlet weak var diceCollectionView: UICollectionView!
var dice:[Int] = [Int]()
override init(frame: CGRect) {
super.init(frame: frame)
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
func setup(loco:EYLocomotive) {
self.diceCollectionView.delegate = self
self.diceCollectionView.dataSource = self
self.diceCollectionView.allowsSelection = false
self.diceCollectionView.allowsMultipleSelection = false
self.diceCollectionView.isUserInteractionEnabled = false
self.diceCollectionView.showsVerticalScrollIndicator = false
self.diceCollectionView.showsHorizontalScrollIndicator = false
self.diceCollectionView.register(UINib(nibName: "EYDiceCollectionViewCell", bundle: nil), forCellWithReuseIdentifier: "EYDiceCollectionViewCell")
// add dummy dice for testing purposes only
for var _ in 1...3 {
let die = Die().roll
dice.append(die)
}
}
The diceCollectionView is the holder of the Dice Imagery.
When we get to to the UICollectionViewDelegate; in the same file;
// MARK: Collection View Delegate
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return dice.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell: EYDiceCollectionViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: "EYDiceCollectionViewCell", for: indexPath) as! EYDiceCollectionViewCell
let dieValue = self.dice[indexPath.row] as Int
let imageFile:String = "die-face-\(dieValue)"
cell.imageView.image = UIImage(named: imageFile)
cell.layoutIfNeeded()
return cell
}
The UICollectionView works fine, the problem comes when I start scrolling horizontally out of the viewport and then scroll back.
Contents of the cell change.
Contents of the cell sometimes change to a different one to the one I'm expecting
Contents of the cell sometimes disappear upon scrolling
What I'd like to know is how can I ensure the contents do not change?
With thanks