UICollectionView and NSFetchedResultsControllerDelegate integration in Swift

UICollection and NSFetchedResultsControllerDelegate integration.swift

var fetchedResultsProcessingOperations: [NSBlockOperation] = []

private func addFetchedResultsProcessingBlock(processingBlock:(Void)->Void) {
	fetchedResultsProcessingOperations.append(NSBlockOperation(block: processingBlock))
}

func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
	
	switch type {
	case .Insert:
		addFetchedResultsProcessingBlock {self.collectionView!.insertItemsAtIndexPaths([newIndexPath!])}
	case .Update:
		addFetchedResultsProcessingBlock {self.collectionView!.reloadItemsAtIndexPaths([indexPath!])}
	case .Move:
		addFetchedResultsProcessingBlock {
			// If installsStandardGestureForInteractiveMovement is on
			// the UICollectionViewController will handle this on its own.
			guard !self.installsStandardGestureForInteractiveMovement else {
				return
			}
			self.collectionView!.moveItemAtIndexPath(indexPath!, toIndexPath: newIndexPath!)
		}
	case .Delete:
		addFetchedResultsProcessingBlock {self.collectionView!.deleteItemsAtIndexPaths([indexPath!])}
	}
	
}

func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {
	
	switch type {
	case .Insert:
		addFetchedResultsProcessingBlock {self.collectionView!.insertSections(NSIndexSet(index: sectionIndex))}
	case .Update:
		addFetchedResultsProcessingBlock {self.collectionView!.reloadSections(NSIndexSet(index: sectionIndex))}
	case .Delete:
		addFetchedResultsProcessingBlock {self.collectionView!.deleteSections(NSIndexSet(index: sectionIndex))}
	case .Move:
		// Not something I'm worrying about right now.
		break
	}
	
}
	
func controllerDidChangeContent(controller: NSFetchedResultsController) {
	collectionView!.performBatchUpdates({ () -> Void in
		for operation in self.fetchedResultsProcessingOperations {
			operation.start()
		}
		}, completion: { (finished) -> Void in
			self.fetchedResultsProcessingOperations.removeAll(keepCapacity: false)
	})
}

deinit {
	// Cancel all block operations when VC deallocates
	for operation in fetchedResultsProcessingOperations {
		operation.cancel()
	}
	
	fetchedResultsProcessingOperations.removeAll()
}