How we migrated Zalando app to Swift3?
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The document outlines the migration process of a codebase from Swift 2.3 to Swift 3 at Zalando, highlighting the challenges faced and changes required during the transition. It discusses team structure, code statistics, common issues encountered such as method signature adjustments, and the strategies employed to address them. The overall migration took almost a month, including a week of vacation, with a focus on error fixing and maintaining consistency in unit and UI tests.
![Readability matters.
Obj-C
[string writeToFile:path atomically:YES encoding:NSUTF8StringEncoding
error:&error];
<= Swift2.3
"SomeLongText".writeToFile(path, atomically: false, encoding:
NSUTF8StringEncoding, error: nil)
Swift3
try! "SomeLongText".write(to: path, atomically: true,
encoding: String.Encoding.utf8)
Swift3
try "SomeLongText".write(to: path, atomically: true,
encoding: .utf8)](https://image.slidesharecdn.com/zalandoswiftmigration-161116095430/85/How-we-migrated-Zalando-app-to-Swift3-3-320.jpg)
![Most occurred cases
• [AnyObject: NSObject] —> [AnyHashable: Any]
• Dropping NS prefix
• Annotating closure with @escaping
• Type casting](https://image.slidesharecdn.com/zalandoswiftmigration-161116095430/85/How-we-migrated-Zalando-app-to-Swift3-27-320.jpg)
How we migrated Zalando app to Swift3?
- 2. Intro to Japanese • 私の名前はビゼです。 • My name is Bj.
- 3. Readability matters. Obj-C [string writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:&error]; <= Swift2.3 "SomeLongText".writeToFile(path, atomically: false, encoding: NSUTF8StringEncoding, error: nil) Swift3 try! "SomeLongText".write(to: path, atomically: true, encoding: String.Encoding.utf8) Swift3 try "SomeLongText".write(to: path, atomically: true, encoding: .utf8)
- 4. • Change or it will. • Different point of view makes you analyse options better
- 5. Key facts at Zalando • 12 iOS engineers • 1 repository • 5 years and counting • Around 1,00,000 Lines of “OUR” Code • 51% Swift • 48% Obj-C
- 6. 1 Migrator
- 12. FFR • Get more error (~ 170). Fix • Fix • Run!
- 13. Fixes • Trivial changes on 95% • 5% required cognitive effort
- 14. Comment • For non trivial fixes, we placed comments
- 20. Fixing More • Fixing Pods / Dependencies • Removed TimePiece, Hamcrest • Migrated ones that didn’t have Swift3 branch yet • Fixing Unit tests, UI tests • Make it run!
- 21. Do we merge to develop? • 2 days for entire team to fix the comments • Do regression test and verify consistency • Bug bash
- 26. How long? • Almost a month. • 1 week vacation
- 27. Most occurred cases • [AnyObject: NSObject] —> [AnyHashable: Any] • Dropping NS prefix • Annotating closure with @escaping • Type casting
- 28. • Parameter renaming. Not called delegates because of nearly matching signature ie. TableViewDelegate
- 29. • Parameter renaming. Not called delegates because of nearly matching signature ie. TableViewDelegate
- 30. • many IBAction didn’t work (when manually merging Swift2.3 to swift3). ie. merging later on. • Private to fileprivate, its everywhere • public to open everywhere, we didnt wanted it to be that way
- 31. New introduction • fileprivate • open • parameter naming • String! as Optional
- 32. Improvements • Removal of C style for loop • Removal of ++ and - - operator • default for closure to @noescape • More on the change-set
- 33. Interesting occurrences • Method signature nearly matches • @discardableResult func …. _ = nextResponder.perform(handler, with: actionInfo) _ = navigationController?.popViewController(animated: true) • 969 warnings. Mostly from unannotated Obj-C API —
- 34. • 私の 名前は ビゼ です。 • My name is Bj. • @kandelvijaya • AnyQuestions?