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Deleting Courses Using Snapshots

If you're interested in working on a more robust deletion implementation, so that tutorials stay deleted from the Queue tab, check out this code you can add to the deleteSelectedItems method that will update the DataSource:

@IBAction func deleteSelectedItems() {
guard let selectedIndexPaths = collectionView.indexPathsForSelectedItems else { return }
let tutorials = selectedIndexPaths.compactMap { dataSource.itemIdentifier(for: $0) }

// Get all of the tutorials in the data source that are currently queued
let queuedTutorials = DataSource.shared.tutorials.flatMap { $0.queuedTutorials }
// Find the queued tutorials that will be deleted from the collection view
let tutorialsToUnqueue = Set(tutorials).intersection(queuedTutorials)
// Set the `isQueued` property to false for each matching tutorial
tutorialsToUnqueue.forEach { $0.isQueued = false }
...

Update Note: This course was originally recorded in November, 2019 using Xcode 11 & iOS 13. The course has been reviewed, and all materials updated to Xcode 12 & iOS 14 as of September, 2020.

Everything is easier using diffable data sources, including deleting items. Learn how to apply changes and animate them in this episode.

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