CoreData has a wonderful tool called NSFetchedResultsController. This tool allows receiving notifications when an object matching a specific set of requirements (NSPredicate) is created or deleted in an NSManagedObjectContext. Whenever such objects are created or deleted, you can tell a corresponding UITableView or UICollectionView to insert/delete rows accordingly.
For a UITableView, it is relatively easy to do. Apple does provide a CoreData Master/Detail project template which has all of the code to do it too.
With a UICollectionView, it is a bit more tricky (because groupped updates are done via a handler instead of using the “beginUpdates/endUpdates” methods).
This project makes it easy for a UICollectionView (and easier for a UITableView) to use the NSFetchedResultsController class in a CoreData project: receive the notifications from the results controller and just forward them to your table or collection view directly.
/* *** Collection View Setup *** */
/* First, how to handle a reload of a cell? */
collectionView.fetchedResultsControllerReloadMode = .handler({ [weak self] cell, object, collectionViewIndexPath, dataSourceIndexPath in
self?.setup(cell: cell as! MyCellType, with: object as! MyObjectType)
})
/* Next, when a cell moves, what to do? Here, we do a move (other solution
* is to delete/insert the cell).
* When a cell is moved, it must be reloaded too. We say we want the
* standard reload mode (the one we have defined above). */
collectionView.fetchedResultsControllerMoveMode = .move(reloadMode: .standard)
/* *** Handling the NSFetchedResultsController notifications *** */
/* We simply forward the methods to the collection view */
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
collectionView.fetchedResultsControllerWillChangeContent()
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
collectionView.fetchedResultsControllerDidChange(section: sectionInfo, atIndex: sectionIndex, forChangeType: type)
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
collectionView.fetchedResultsControllerDidChange(object: anObject, atIndexPath: indexPath, forChangeType: type, newIndexPath: newIndexPath)
}
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
collectionView.fetchedResultsControllerDidChangeContent(endUpdatesHandler: nil)
}The project is compatible with Carthage. You can also simply copy the two UICollectionView extensions and the UITableView extension in your project.