CoreData如何使用nsfetchedcontroller在UICollectionView中显示

let fetchRequest: NSFetchRequest<YourEntity> = YourEntity.fetchRequest()
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "yourSortKey", ascending: true)]

let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: yourManagedObjectContext, sectionNameKeyPath: nil, cacheName: nil)
fetchedResultsController.delegate = self

extension YourViewController: NSFetchedResultsControllerDelegate {
    func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
        collectionView?.beginUpdates()
    }

    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
        switch type {
        case .insert:
            collectionView?.insertItems(at: [newIndexPath!])
        case .delete:
            collectionView?.deleteItems(at: [indexPath!])
        case .update:
            collectionView?.reloadItems(at: [indexPath!])
        case .move:
            collectionView?.moveItem(at: indexPath!, to: newIndexPath!)
        }
    }

    func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
        collectionView?.endUpdates()
    }
}

extension YourViewController: UICollectionViewDataSource {
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return fetchedResultsController.sections?.count ?? 0
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return fetchedResultsController.sections?[section].numberOfObjects ?? 0
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "YourCellIdentifier", for: indexPath) as! YourCell
        let object = fetchedResultsController.object(at: indexPath)
        // 配置cell的内容
        return cell
    }
}