Swift，iOS15，UIKit，CollectionView header问题

Question

我正在测试iOS15和UIKit的一些新功能。 我遇到了一些问题，不确定如何解决。 我没有更改该代码。 这只是一段与 iOS 14 完美配合的代码，现在更新我的目标后，它会抛出错误。

Xcode 在为dataSource返回类型为UICollectionElementKindSectionHeader的UICollectionView的自定义 header时崩溃。 这是我的代码：

private func configureDataSource() {
      dataSource = UICollectionViewDiffableDataSource<Section, Follower>(collectionView: collectionView, cellProvider: { (collectionView, indexPath, followers) -> UICollectionViewCell? in
         let cell = collectionView.dequeueReusableCell(withReuseIdentifier: FollowerCell.reuseId, for: indexPath) as! FollowerCell
         cell.set(on: followers)
         return cell
      })
      
      dataSource.supplementaryViewProvider = { (collectionView, kind, indexPath) in
         let header = collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionView.elementKindSectionHeader,
                                                                      withReuseIdentifier: FollowersCollectionHeaderView.reuseId,
                                                                      for: indexPath) as! FollowersCollectionHeaderView
         
         header.set(with: self.user)
         return header
      }
   }

日志说：

从 -collectionView:viewForSupplementaryElementOfKind:atIndexPath: 返回的视图与它所使用的元素种类不匹配。 当请求元素种类“FollowersCollectionHeaderView”的视图时，数据源使为元素种类“UICollectionElementKindSectionHeader”注册的视图出队。

我确实将UICollectionElementKindSectionHeader 转换为FollowersCollectionHeaderView ，因此我不确定这里的问题是什么。

我看过WWDC21 what's new in UIKit但没有看到任何提及该特定代码的任何更改。

有什么建议，要在该代码中修复什么？

Answer 1

这是我想出的部分解决方案。 Apple 建议使用对象的 ID 作为 collectionView 单元格的参考。

enum Section { case main }


var dataSource: UICollectionViewDiffableDataSource<Section, Follower.ID>!

// MARK: - Collection View configurations
    fileprivate lazy var collectionView: UICollectionView = {
        let collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: UIHelper.createCompositionalLayout())
        collectionView.delegate = self
        collectionView.backgroundColor = .systemBackground
        collectionView.register(FollowersCollectionHeaderView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: FollowersCollectionHeaderView.reuseId)
        view.addSubview(collectionView)
        return collectionView
    }()
    
    fileprivate lazy var snapshot: NSDiffableDataSourceSnapshot<Section, Follower.ID> = {
        var snapshot = NSDiffableDataSourceSnapshot<Section, Follower.ID>()
        snapshot.appendSections([.main])
        let itemIdentifiers = followers.map { $0.id }
        snapshot.appendItems(itemIdentifiers, toSection: .main)
        dataSource.apply(snapshot, animatingDifferences: true)
        return snapshot
    }()
    
    fileprivate func updateData(with followers: [Follower]) {
        snapshot = NSDiffableDataSourceSnapshot<Section, Follower.ID>()
        snapshot.appendSections([.main])
        let itemIdentifiers = followers.map { $0.id }
        snapshot.appendItems(itemIdentifiers, toSection: .main)
        dataSource.apply(snapshot, animatingDifferences: true)
    }
    
    fileprivate func configureDataSource() {
        let cellRegistration = UICollectionView.CellRegistration<FollowerCell, Follower.ID> { [weak self]
            cell, indexPath, followerID in
            guard let self = self else { return }
            
            let followerArray = self.followers.filter { $0.id == followerID }
            
            if let follower = followerArray.first {
                cell.set(on: follower)
            }
        }
        
        dataSource = UICollectionViewDiffableDataSource<Section, Follower.ID>(collectionView: collectionView) {
            collectionView, indexPath, itemIdentifier in
            
            return collectionView.dequeueConfiguredReusableCell(using: cellRegistration,
                                                                for: indexPath,
                                                                item: itemIdentifier)
        }
        
        let headerRegistration = createSectionHeaderRegistration()
        dataSource.supplementaryViewProvider = { collectionView, elementKind, indexPath in
            return collectionView.dequeueConfiguredReusableSupplementary(using: headerRegistration, for: indexPath)
        }
    }
    
    fileprivate func createSectionHeaderRegistration() -> UICollectionView.SupplementaryRegistration<FollowersCollectionHeaderView> {
        return UICollectionView.SupplementaryRegistration<FollowersCollectionHeaderView>(
            elementKind: FollowersCollectionHeaderView.reuseId) { [weak self] supplementaryView, elementKind, indexPath in
            guard let self = self else { return }
            supplementaryView.set(with: self.user)
        }
    }

Answer 2

使用UICollectionView.elementKindSectionHeader而不是您创建的字符串

override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
    
    guard let header = collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: "headerView", for: indexPath) as? TitleDetailsHeaderView else { return UICollectionReusableView() }

return header
}