UICollectionView and NSFetchedResultsControllerDelegate integration in Swift

UICollection and NSFetchedResultsControllerDelegate integration.swift

// I just implemented that with Swift. So I would like to share my implementation.
// First initialise an array of NSBlockOperations:
        var blockOperations: [NSBlockOperation] = []

    
// In the did change object method:
        func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
        
        if type == NSFetchedResultsChangeType.Insert {
            println("Insert Object: \(newIndexPath)")
            
            blockOperations.append(
                NSBlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.insertItemsAtIndexPaths([newIndexPath!])
                    }
                })
            )
        }
        else if type == NSFetchedResultsChangeType.Update {
            println("Update Object: \(indexPath)")
            blockOperations.append(
                NSBlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.reloadItemsAtIndexPaths([indexPath!])
                    }
                })
            )
        }
        else if type == NSFetchedResultsChangeType.Move {
            println("Move Object: \(indexPath)")
            
            blockOperations.append(
                NSBlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.moveItemAtIndexPath(indexPath!, toIndexPath: newIndexPath!)
                    }
                })
            )
        }
        else if type == NSFetchedResultsChangeType.Delete {
            println("Delete Object: \(indexPath)")
            
            blockOperations.append(
                NSBlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.deleteItemsAtIndexPaths([indexPath!])
                    }
                })
            )
        }
    }

// In the did change section method:
    func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {
        
        if type == NSFetchedResultsChangeType.Insert {
            println("Insert Section: \(sectionIndex)")
            
            blockOperations.append(
                NSBlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.insertSections(NSIndexSet(index: sectionIndex))
                    }
                })
            )
        }
        else if type == NSFetchedResultsChangeType.Update {
            println("Update Section: \(sectionIndex)")
            blockOperations.append(
                NSBlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.reloadSections(NSIndexSet(index: sectionIndex))
                    }
                })
            )
        }
        else if type == NSFetchedResultsChangeType.Delete {
            println("Delete Section: \(sectionIndex)")
            
            blockOperations.append(
                NSBlockOperation(block: { [weak self] in
                    if let this = self {
                        this.collectionView!.deleteSections(NSIndexSet(index: sectionIndex))
                    }
                })
            )
        }
    }

// And finally, in the did controller did change content method:
    func controllerDidChangeContent(controller: NSFetchedResultsController) {        
        collectionView!.performBatchUpdates({ () -> Void in
            for operation: NSBlockOperation in self.blockOperations {
                operation.start()
            }
        }, completion: { (finished) -> Void in
            self.blockOperations.removeAll(keepCapacity: false)
        })
    }

// I personally added some code in the deinit method as well, in order to cancel the operations when the ViewController is about to get deallocated:
    deinit {
        // Cancel all block operations when VC deallocates
        for operation: NSBlockOperation in blockOperations {
            operation.cancel()
        }
        
        blockOperations.removeAll(keepCapacity: false)
    }

Thank you for sharing. I'm using Swift 3 and Xcode 8.0 to build a UICollectionView with NSFetchedResultsController integration, this Gist was working fine for me on older versions of Swift an iOS, however on iOS 10 i receive the following error message, which gets called in controllerDidChangeContent.

This application is modifying the autolayout engine from a background thread after the engine was accessed from the main thread.

Has anybody upgraded to the latest version of Swift and Xcode and has a working version of UICollectionView + NSFetchedResultsController?

hey all, just converted the above to swift 3 : https://gist.github.com/nazywamsiepawel/e88790a1af1935ff5791c9fe2ea19675