DifferenceKit in Action

try! Swift Tokyo 2020 Meetup!!
2020/01/21
Twitter hashtag: #tryswiftconf_meetup

Transcript

1. DifferenceKit in Action try! Swift Tokyo 2020 Meetup!! Jan 2020
2. Ryo Aoyama CyberAgent, Inc. CATS productivity team Twitter: @ra1028fe5 GitHub: @ra1028 OSS: DifferenceKit, Carbon, swift-mod, etc…
3. DifferenceKit https://github.com/ra1028/DifferenceKit Ver: 1.1.5 Star: 2.3k Fork: 133 A fast and flexible O(n) difference algorithm framework for Swift collection.
4. Works on many production app LINE Mercari Uber CyberAgent Yahoo Japan PayPay dely NIKKEI and more… eureka
5. Why we use diffing algorithm • For performance • For beautiful animation • For declarative programming • For business logic segregation
6. Ordered N-items List UI
7. When insert an item to the list, reloadDate() will calculates for all items. It’s not efficient Reload
8. UI calculations are very slow and will force the main thread. Reload Slow Slow Slow Slow
9. Improving list UI performance by updating only the differences. Reload Slow
10. performBatchUpdates can partially update items with animations let deleteIndexPaths: [IndexPath] let insertIndexPaths: [IndexPath] let moveIndexPaths: (from: IndexPath, to: IndexPath) let reloadIndexPaths: [IndexPath] tableView.performBatchUpdates({ tableView.deleteRows(at: deleteIndexPaths, with: .automatic) tableView.insertRows(at: insertIndexPaths, with: .automatic) tableView.moveRow(at: moveIndexPaths.from, to: moveIndexPaths.to) tableView.reloadRows(at: reloadIndexPaths, with: .automatic) })
11. Now, do you know which item was inserted?
12. How can I programmatically know how the item array requested to the network has changed?
13. Diffing algorithm Calculates the diffs before and after updating the array. https://en.wikipedia.org/wiki/Diff Wiki:
14. DifferenceKit let source: [Item] let target: [Item] let changeset = StagedChangeset(source: source, target: target) tableView.reload(using: changeset, with: .automatic) { data in self.data = data }
15. Paul Heckel’s Algorithm DifferenceKit uses… Paper: A technique for isolating differences between files https://dl.acm.org/doi/10.1145/359460.359467 With O(N) complexity, linear function time can be expected regardless of data size and changes. Ideal for UI calculations, IMO.
16. Paul Heckel’s Algorithm DifferenceKit uses… Optimizations in terms of + • Algorithm • Swift lang
17. Major Diffing Algorithms Author Myers Wu Heckel complexity O(ND) O(NP) O(N) insert ✅ ✅ ✅ delete ✅ ✅ ✅ move ⚠ ⚠ ✅ update ❌ ❌ ✅ shortest? Yes Yes No http://www.xmailserver.org/diff2.pdf http://documents.scribd.com/docs/10ro9oowpo1h81pgh1as.pdf https://publications.mpi-cbg.de/Wu_1990_6334.pdf
18. Swift Library Comparisons Disclaimer: These DO NOT compete for the “Best” of the library.
19. Library Algorithms
20. Performance Comparison • 3x slower • 20x slower • 7x slower • 18x slower • 4500x slower • 5400x slower • 140x slower From 100,000 elements to 10,000 deleted, 10,000 inserted and 2,000 shuffled BLAZING FAST !
21. Functionality Comparison Supported Collection
22. Functionality Comparison Supported Element Diff
23. Functionality Comparison Supported Section Diff
24. DifferenceKit in Future
25. DiffableDataSource https://developer.apple.com/videos/play/wwdc2019/220/ is pretty solid solution for diffing in list UI items. But, DifferenceKit is more loosely-coupled, white-boxed and for any usage (mainly UI).
26. SwiftUI https://developer.apple.com/xcode/swiftui/ New generation, personally, I hope SwiftUI will eliminate the DifferenceKit. Currently, SwiftUI.List has no customizability. We should use UITableView and UICollectionView as before. DifferenceKit will be useful for a while.
27. Thanks Twitter: @ra1028fe5 GitHub: @ra1028 Ryo Aoyama