UICollectionView + NSFetchedResultsController Swift 5

UICollectionView + NSFetchedResultsController.swift

// MARK: NSFetchedResultsController
extension ViewController: NSFetchedResultsControllerDelegate {
    
    var blockOperations: [BlockOperation] = []
    
    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
        switch type {
            case .insert:
                let insertBlock: () -> Void = { [weak self] in self?.collectionView?.insertItems(at: [newIndexPath!]) }
                blockOperations.append(BlockOperation(block: insertBlock))
            case .delete:
                let deleteBlock: () -> Void = { [weak self] in self?.collectionView?.deleteItems(at: [indexPath!]) }
                blockOperations.append(BlockOperation(block: deleteBlock))
            case .update:
                let reloadBlock: () -> Void = { [weak self] in self?.collectionView?.reloadItems(at: [indexPath!]) }
                blockOperations.append(BlockOperation(block: reloadBlock))
            case .move:
                let moveBlock: () -> Void = { [weak self] in self?.collectionView?.moveItem(at: indexPath!, to: newIndexPath!) }
                blockOperations.append(BlockOperation(block: moveBlock))
            @unknown default:
                fatalError()
        }
    }
    
    public func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
        switch type {
            case .insert:
                let insertBlock: () -> Void = { [weak self] in self?.collectionView?.insertSections(IndexSet(integer: sectionIndex)) }
                blockOperations.append(BlockOperation(block: insertBlock))
            case .delete:
                let deleteBlock: () -> Void = { [weak self] in self?.collectionView?.deleteSections(IndexSet(integer: sectionIndex))}
                blockOperations.append(BlockOperation(block: deleteBlock))
            case .update:
                let reloadBlock: () -> Void = { [weak self] in self?.collectionView?.reloadSections(IndexSet(integer: sectionIndex))}
                blockOperations.append(BlockOperation(block: reloadBlock))
            case .move: break
            @unknown default:
                fatalError()
        }
    }
    
    func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
        collectionView?.performBatchUpdates({
            blockOperations.forEach({ $0.start() })
        }, completion: { _ in self.blockOperations.removeAll() })
    }
    
    deinit {
        blockOperations.forEach({ $0.cancel() })
        blockOperations.removeAll()
    }
}