NSFetchedResultsContollerDelegate for CollectionView

Question

I\'d like to use the NSFetchedResultsControllerRelegate in a CollectionViewController. Therefore I just changed the method for the TableViewController for the CollectionView

Answer 1

Here's a bit of Swift that works with UICollectionViewController's installsStandardGestureForInteractiveMovement and is a somewhat DRYed up and switches on the installsStandardGestureForInteractiveMovement so that all the code paths are obvious. It's the same overall pattern as Plot's code.

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 {
    for operation in fetchedResultsProcessingOperations {
        operation.cancel()
    }

    fetchedResultsProcessingOperations.removeAll()
}