 
 // MARK: CollectionStackViewController
 
-protocol CollectionStackViewControllerDelegate {
+protocol CollectionStackViewControllerDelegate: class {
   func controllerDidSelected(index index: Int)
 }
 

  }
  
  override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
    delegate.controllerDidSelected(index: indexPath.row)
    
    guard let currentCell = collectionView.cellForItemAtIndexPath(indexPath) else {
      return

  private var screens: [UIImage]
  private let overlay: Float
  
  weak var delegate: CollectionStackViewControllerDelegate?
  
  init(images: [UIImage],
    delegate: CollectionStackViewControllerDelegate?,
    overlay: Float,
    scaleRatio: Float,
    scaleValue: Float,
