Incorrect animation when reordering tableview with new iOS 11 APIs

Question

I'm using the new drag and drop APIs on iOS 11 to reorder cells in a tableview inside the same app.

Here's my implementation for UITableViewDragDelegate and UITableViewDropDelegate:

extension TasksViewController: UITableViewDragDelegate {
    func tableView(_ tableView: UITableView, itemsForBeginning session: UIDragSession, at indexPath: IndexPath) -> [UIDragItem] {
        let string = tasks[indexPath.row]
        guard let data = string.data(using: .utf8) else { return [] }
        let itemProvider = NSItemProvider(item: data as NSData, typeIdentifier: kUTTypePlainText as String)
        let item = UIDragItem(itemProvider: itemProvider)
        item.localObject = string

        return [item]
    }
}

extension TasksViewController: UITableViewDropDelegate {
    func tableView(_ tableView: UITableView, canHandle session: UIDropSession) -> Bool {
        return true
    }

    func tableView(_ tableView: UITableView, dropSessionDidUpdate session: UIDropSession, withDestinationIndexPath destinationIndexPath: IndexPath?) -> UITableViewDropProposal {

        if session.localDragSession != nil { // Drag originated from the same app.
            return UITableViewDropProposal(operation: .move, intent: .insertAtDestinationIndexPath)
        }

        return UITableViewDropProposal(operation: .cancel, intent: .unspecified)
    }

    func tableView(_ tableView: UITableView, performDropWith coordinator: UITableViewDropCoordinator) {
        guard let destinationIndexPath = coordinator.destinationIndexPath,
            let dragItem = coordinator.items.first?.dragItem,
            let task = dragItem.localObject as? String,
            let sourceIndexPath = coordinator.items.first?.sourceIndexPath else {
                return
        }

        tableView.performBatchUpdates({
            self.tasks.remove(at: sourceIndexPath.row)
            self.tasks.insert(task, at: destinationIndexPath.row)

            tableView.deleteRows(at: [sourceIndexPath], with: .none)
            tableView.insertRows(at: [destinationIndexPath], with: .none)
        })

        coordinator.drop(dragItem, toRowAt: destinationIndexPath)
    }
}

This works fine, but has a weird glitch. When the last cell is being dragged, as soon as it's dropped, it appears at the bottom of the tableview for a split second then disappears.

What am I missing here?

Answer 1

Just change table deletion animation to .automatic, like so:

tableView.deleteRows(at: [sourceIndexPath], with: .automatic)

After that there won't be that weird animation.