Don't use NSFetchedResultsController for items list
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@ -189,6 +189,22 @@ extension HomeViewController {
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return req
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}
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var idFetchRequest: NSFetchRequest<NSManagedObjectID> {
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let req = NSFetchRequest<NSManagedObjectID>(entityName: "Item")
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req.resultType = .managedObjectIDResultType
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switch self {
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case .unread:
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req.predicate = NSPredicate(format: "read = NO")
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case .all:
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break
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case .group(let group):
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req.predicate = NSPredicate(format: "feed in %@", group.feeds!)
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case .feed(let feed):
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req.predicate = NSPredicate(format: "feed = %@", feed)
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}
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return req
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}
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var countFetchRequest: NSFetchRequest<Reader.Item>? {
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let req = Reader.Item.fetchRequest()
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switch self {
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@ -229,7 +245,7 @@ extension HomeViewController: UICollectionViewDelegate {
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guard let item = dataSource.itemIdentifier(for: indexPath) else {
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return
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}
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let vc = ItemsViewController(fetchRequest: item.fetchRequest, fervorController: fervorController)
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let vc = ItemsViewController(fetchRequest: item.idFetchRequest, fervorController: fervorController)
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vc.title = item.title
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vc.delegate = itemsDelegate
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show(vc, sender: nil)
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@ -241,7 +257,7 @@ extension HomeViewController: UICollectionViewDelegate {
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return nil
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}
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return UIContextMenuConfiguration(identifier: nil, previewProvider: {
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return ItemsViewController(fetchRequest: item.fetchRequest, fervorController: self.fervorController)
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return ItemsViewController(fetchRequest: item.idFetchRequest, fervorController: self.fervorController)
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}, actionProvider: nil)
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}
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@ -18,14 +18,16 @@ class ItemsViewController: UIViewController {
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weak var delegate: ItemsViewControllerDelegate?
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let fervorController: FervorController
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let fetchRequest: NSFetchRequest<Item>
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let fetchRequest: NSFetchRequest<NSManagedObjectID>
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private var collectionView: UICollectionView!
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private var resultsController: NSFetchedResultsController<Item>!
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private var dataSource: UICollectionViewDiffableDataSource<Section, NSManagedObjectID>!
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private var batchUpdates: [() -> Void] = []
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init(fetchRequest: NSFetchRequest<Item>, fervorController: FervorController) {
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init(fetchRequest: NSFetchRequest<NSManagedObjectID>, fervorController: FervorController) {
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precondition(fetchRequest.entityName == "Item")
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self.fervorController = fervorController
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self.fetchRequest = fetchRequest
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@ -47,12 +49,11 @@ class ItemsViewController: UIViewController {
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configuration.backgroundColor = .clear
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let layout = UICollectionViewCompositionalLayout.list(using: configuration)
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collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
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collectionView.delegate = self
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collectionView.dataSource = self
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collectionView.translatesAutoresizingMaskIntoConstraints = false
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collectionView.register(ItemCollectionViewCell.self, forCellWithReuseIdentifier: "itemCell")
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view.addSubview(collectionView)
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dataSource = createDataSource()
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NSLayoutConstraint.activate([
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collectionView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor),
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collectionView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor),
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@ -61,69 +62,116 @@ class ItemsViewController: UIViewController {
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])
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fetchRequest.sortDescriptors = [NSSortDescriptor(key: "published", ascending: false)]
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fetchRequest.fetchBatchSize = 20
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resultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: fervorController.persistentContainer.viewContext, sectionNameKeyPath: nil, cacheName: nil)
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resultsController.delegate = self
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try! resultsController.performFetch()
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do {
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let ids = try fervorController.persistentContainer.viewContext.fetch(fetchRequest)
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var snapshot = NSDiffableDataSourceSnapshot<Section, NSManagedObjectID>()
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snapshot.appendSections([.items])
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snapshot.appendItems(ids, toSection: .items)
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dataSource.apply(snapshot, animatingDifferences: false)
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NotificationCenter.default.addObserver(self, selector: #selector(managedObjectsDidChange), name: .NSManagedObjectContextObjectsDidChange, object: fervorController.persistentContainer.viewContext)
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} catch {
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let alert = UIAlertController(title: "Error fetching items", message: error.localizedDescription, preferredStyle: .alert)
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alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
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present(alert, animated: true)
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}
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}
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}
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extension ItemsViewController: UICollectionViewDataSource {
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func numberOfSections(in collectionView: UICollectionView) -> Int {
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return 1
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}
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func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
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return resultsController.fetchedObjects?.count ?? 0
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}
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func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
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let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "itemCell", for: indexPath) as! ItemCollectionViewCell
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private func createDataSource() -> UICollectionViewDiffableDataSource<Section, NSManagedObjectID> {
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let itemCell = UICollectionView.CellRegistration<ItemCollectionViewCell, NSManagedObjectID> { [unowned self] cell, indexPath, itemIdentifier in
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cell.delegate = self
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cell.scrollView = collectionView
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cell.updateUI(item: resultsController.fetchedObjects![indexPath.row])
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return cell
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cell.scrollView = self.collectionView
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let item = self.fervorController.persistentContainer.viewContext.object(with: itemIdentifier) as! Item
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cell.updateUI(item: item)
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}
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return UICollectionViewDiffableDataSource(collectionView: collectionView) { collectionView, indexPath, itemIdentifier in
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return collectionView.dequeueConfiguredReusableCell(using: itemCell, for: indexPath, item: itemIdentifier)
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}
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}
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extension ItemsViewController: NSFetchedResultsControllerDelegate {
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func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
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batchUpdates = []
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@objc private func managedObjectsDidChange(_ notification: Notification) {
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let inserted = notification.userInfo?[NSInsertedObjectsKey] as? NSSet
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let updated = notification.userInfo?[NSUpdatedObjectsKey] as? NSSet
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let deleted = notification.userInfo?[NSDeletedObjectsKey] as? NSSet
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// managed objectss from the notification are tied to the thread it was delivered on
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// so get the published dates and evaluate the predicate here
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let insertedItems = inserted?.compactMap { $0 as? Item }.filter { fetchRequest.predicate?.evaluate(with: $0) ?? true }.map { ($0, $0.published) }
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var snapshot = self.dataSource.snapshot()
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if let updated = updated {
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snapshot.reconfigureItems(updated.compactMap { ($0 as? Item)?.objectID })
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}
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func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
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collectionView.performBatchUpdates {
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for update in self.batchUpdates {
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update()
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if let deleted = deleted {
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snapshot.deleteItems(deleted.compactMap { ($0 as? Item)?.objectID })
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}
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if let insertedItems = insertedItems {
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self.fervorController.persistentContainer.performBackgroundTask { ctx in
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// for newly inserted items, the ctx doesn't have the published date so we check the data we got from the notification
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func publishedForItem(_ id: NSManagedObjectID) -> Date? {
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if let (_, pub) = insertedItems.first(where: { $0.0.objectID == id }) {
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return pub
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} else {
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return (ctx.object(with: id) as! Item).published
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}
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}
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// clear to prevent retain cycles
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batchUpdates = []
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// todo: this feels inefficient
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for (inserted, insertedPublished) in insertedItems {
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// todo: uhh, what does sql do if the published date is nil?
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guard let insertedPublished = insertedPublished else {
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snapshot.insertItems([inserted.objectID], beforeItem: snapshot.itemIdentifiers.first!)
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continue
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}
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func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
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guard let indexPath = indexPath else {
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return
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var index = 0
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while index < snapshot.itemIdentifiers.count,
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let pub = publishedForItem(snapshot.itemIdentifiers[index]),
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insertedPublished < pub {
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index += 1
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}
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batchUpdates.append {
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switch type {
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case .insert:
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self.collectionView.insertItems(at: [indexPath])
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case .delete:
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self.collectionView.deleteItems(at: [indexPath])
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case .move:
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if let newIndexPath = newIndexPath {
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self.collectionView.moveItem(at: indexPath, to: newIndexPath)
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}
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case .update:
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self.collectionView.reloadItems(at: [indexPath])
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@unknown default:
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break
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// index is the index of the first item which the inserted one was published after
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// (i.e., the item that should appear immediately after inserted in the list)
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if index == snapshot.itemIdentifiers.count {
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snapshot.appendItems([inserted.objectID], toSection: .items)
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} else {
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snapshot.insertItems([inserted.objectID], beforeItem: snapshot.itemIdentifiers[index])
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}
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}
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DispatchQueue.main.async {
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self.dataSource.apply(snapshot, animatingDifferences: true)
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}
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}
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} else {
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DispatchQueue.main.async {
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self.dataSource.apply(snapshot, animatingDifferences: true)
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}
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}
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}
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}
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extension ItemsViewController {
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enum Section: Hashable {
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case items
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}
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}
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extension ItemsViewController: UICollectionViewDelegate {
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func collectionView(_ collectionView: UICollectionView, contextMenuConfigurationForItemAt indexPath: IndexPath, point: CGPoint) -> UIContextMenuConfiguration? {
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let item = resultsController.fetchedObjects![indexPath.row]
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guard let id = dataSource.itemIdentifier(for: indexPath) else {
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return nil
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}
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let item = fervorController.persistentContainer.viewContext.object(with: id) as! Item
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// let item = resultsController.fetchedObjects![indexPath.row]
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return UIContextMenuConfiguration(identifier: nil, previewProvider: {
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ReadViewController(item: item, fervorController: self.fervorController)
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}, actionProvider: { _ in
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