I was trying to have a secondary collection view with circle images above (y axis) the functioning collection view but its crashing and throwing this error Error code: could not dequeue a view of kind: UICollectionElementKindCell with identifier CircleCollectionViewCell - must register a nib or a class for the identifier or connect a prototype cell in a storyboard ViewController code: // //  ViewController.swift //  Main_app // //  Created by Kushagr Agarwal on 23/08/21. // import UIKit class ViewController: UIViewController {     @IBOutlet var collectionView: UICollectionView!          @IBOutlet var topCollectionView: UICollectionView!          @IBOutlet weak var Leading: NSLayoutConstraint!          @IBOutlet weak var Trailing: NSLayoutConstraint!          @IBOutlet private weak var Menubutton: UIButton!     var menuOut = false               override func viewDidLoad() {         super.viewDidLoad()         // Do any additional setup after loading the view.         //self.navigationItem.titleView = UIImageView(image: UIImage(named: "Logo"))                  collectionView.register(MiddleCollectionViewCell.nib(), forCellWithReuseIdentifier: MiddleCollectionViewCell.identifier)                  collectionView.delegate=self         collectionView.dataSource=self                  topCollectionView.register(CircleCollectionViewCell.self, forCellWithReuseIdentifier: CircleCollectionViewCell.identifier)         topCollectionView.delegate=self         topCollectionView.dataSource=self //       Menu //       start                  let destructiveAction = UIAction(title: "Delete",image: UIImage(systemName: "nosign") , attributes: .destructive) { (_) in             print("Delete")         }                  let menu = UIMenu(title: "", children: [             UIAction (title: "Add New", image: UIImage(systemName: "plus.circle"), handler: { _ in  }),             UIAction (title: "Manage", image: UIImage(systemName: "hammer"), handler: { _ in  }),             destructiveAction         ])         self.Menubutton.menu = menu //    Menu end     } // Menu animation     @IBAction func MenuTap(_ sender: Any) {         if menuOut == false {             Leading.constant = -150             Trailing.constant = 150             menuOut = true         }         else{             Leading.constant = 0             Trailing.constant = 0             menuOut = false         }         UIView.animate(withDuration: 0.2, delay: 0.0 , options: .curveEaseIn,animations: {             self.view.layoutIfNeeded()         }){(animationComplete) in             print("Animation Completed")         }     } // Menu animation ends } // used for upper collection view extension ViewController: UICollectionViewDelegate {          func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {         collectionView.deselectItem(at: indexPath, animated: true )         print("btn tapped")              }           } extension ViewController: UICollectionViewDataSource {     func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {         return 12     }     func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {         let cell = collectionView.dequeueReusableCell(withReuseIdentifier: MiddleCollectionViewCell.identifier, for: indexPath) as! MiddleCollectionViewCell         let topcell = collectionView.dequeueReusableCell(withReuseIdentifier: CircleCollectionViewCell.identifier, for: indexPath) as! CircleCollectionViewCell         topcell.configure(with: "")                  cell.configure(with: UIImage(named: "four")!)         return cell; topcell     } } //extension ViewController: UICollectionViewDelegateFlowLayout { // //}

What follows is about tvOS 15 but may also apply to iOS 15. Our app may display several types of UICollectionView cells and it depends on the content sent by our backend. Prior to tvOS 15, we used to lazily instantiate UICollectionView cell registrations when needed for the first time while building a UICollectionViewDiffableDataSource. Eventually, each cell registration is only instantiated once (or never). Now tvOS 15 throws an exception when doing so, pretending to prevent the app from creating a new cell registration each time. And it does not care whether it's actually a new cell registration each time or one that is lazily instantiated once. Here is the exception: *** Assertion failure in -[UICollectionView dequeueConfiguredReusableCellWithRegistration:forIndexPath:item:], UICollectionView.m:7413 *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Attempted to dequeue a cell using a registration that was created inside -collectionView:cellForItemAtIndexPath: or inside a UICollectionViewDiffableDataSource cell provider. Creating a new registration each time a cell is requested will prevent reuse and cause created cells to remain inaccessible in memory for the lifetime of the collection view. Registrations should be created up front and reused. Registration: <UICollectionViewCellRegistration: 0x6000000f8c60>' I understand the concern but lazy instantiation is a thing and it should not be for forbidden for the sake of best practices that are not related to it. In my humble opinion, this assert should be removed and apps should be allowed to create cell registrations on the fly.