👀 Views: 1307 💬 Answers: 1 📅 Created: 2025-06-09

swift uicollectionview ios

I'm working with a frustrating scenario with UICollectionView when implementing a Diffable Data Source in my iOS app (Xcode 14, targeting iOS 16). I've set up my collection view to display a list of items, but I keep seeing stale data in the cells after they are reused. I thought using the Diffable Data Source would prevent this, but it seems like the cells are not being correctly updated after a data change. Here's a simplified version of my setup: ```swift import UIKit struct Item: Hashable { let id: UUID let title: String } class MyViewController: UIViewController, UICollectionViewDelegate { var collectionView: UICollectionView! var dataSource: UICollectionViewDiffableDataSource<Section, Item>! enum Section { case main } var items: [Item] = [] override func viewDidLoad() { super.viewDidLoad() configureCollectionView() configureDataSource() loadInitialData() } func configureCollectionView() { let layout = UICollectionViewFlowLayout() collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout) collectionView.delegate = self collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "cell") view.addSubview(collectionView) } func configureDataSource() { dataSource = UICollectionViewDiffableDataSource<Section, Item>(collectionView: collectionView) { (collectionView, indexPath, item) -> UICollectionViewCell? in let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) cell.backgroundColor = .blue // Incorrectly setting the title, demonstrating the question cell.contentView.subviews.forEach { $0.removeFromSuperview() } let label = UILabel(frame: cell.contentView.bounds) label.text = item.title cell.contentView.addSubview(label) return cell } } func loadInitialData() { items = [Item(id: UUID(), title: "Item 1"), Item(id: UUID(), title: "Item 2")] var snapshot = NSDiffableDataSourceSnapshot<Section, Item>() snapshot.appendSections([.main]) snapshot.appendItems(items) dataSource.apply(snapshot, animatingDifferences: true) } func updateData() { items[0] = Item(id: items[0].id, title: "Updated Item 1") var snapshot = dataSource.snapshot() snapshot.reloadItems([items[0]]) dataSource.apply(snapshot, animatingDifferences: true) } } ``` I am calling `updateData()` to modify the first item, but when I run this, I still see the old title in the corresponding cell instead of "Updated Item 1". I even tried to reset the content of the cell in the closure for `cellForItemAt` to ensure it's always displaying the right data. I've confirmed the `items` array is correctly updated, and when I debug, it shows the correct values. However, the UI seems to not reflect these changes. Has anyone experienced similar issues with Diffable Data Source, or am I missing something in my implementation? Any insights would be greatly appreciated! I'm on Windows 11 using the latest version of Swift.