Convert your legacy (Android) app to Kotlin!

From my talk at Code Talks 2017 (https://www.codetalks.de/)
Tips & Tricks for Java-To-Kotlin conversion (live coding)

Transcript

1. Convert your legacy (Android) app to Kotlin! Lovis Möller @lovisbrot #codetalkshh
2. Kotlin Lovis Möller @lovisbrot #codetalkshh
3. Kotlin • Developed by JetBrains Lovis Möller @lovisbrot #codetalkshh
4. Kotlin • Developed by JetBrains • Concise & Expressive Lovis Möller @lovisbrot #codetalkshh
5. Kotlin • Developed by JetBrains • Concise & Expressive • Pragmatic & Secure Lovis Möller @lovisbrot #codetalkshh
6. Kotlin • Developed by JetBrains • Concise & Expressive • Pragmatic & Secure • 100% interoperable with Java Lovis Möller @lovisbrot #codetalkshh
7. Kotlin • Developed by JetBrains • Concise & Expressive • Pragmatic & Secure • 100% interoperable with Java • Easy to learn for Java developers Lovis Möller @lovisbrot #codetalkshh
8. Live Demo Lovis Möller @lovisbrot #codetalkshh Example App: Thesaurus • Enter a word • See synonym results • Display errors, if any https://github.com/lmller/codetalks2017
9. Live Demo Lovis Möller @lovisbrot #codetalkshh 1. Java 2. Kotlin Dependencies 3. Model Classes 4. Api & Dependency Injection 5. Android Classes 6. Domain: ViewModels, Presenters,…
10. More Tricks Lovis Möller @lovisbrot #codetalkshh Replace oldskool GoF patterns with Kotlin Builder  apply function (or named constructor args) Decorator  Extension functions / function composition Interpreter  sealed classes Iterator  operator functions get() and iterator() Observer  Observable delegate Prototype  data classes Singleton  object declaration Strategy  functions Template Method  (top level) functions Visitor  Pattern matching / when https://github.com/lmller/gof-in-kotlin
11. More Tricks Lovis Möller @lovisbrot #codetalkshh Write your own extension functions fun ImageView.setImageUrl(url: String) { Picasso.with(context).load(url).into(this) } imageView.setImageUrl("http://...")
12. More Tricks Lovis Möller @lovisbrot #codetalkshh Write your own extension functions fun View.fadeIn() = animate().alpha(1f).setDuration(300)
 fun View.fadeOut() = animate().alpha(0f).setDuration(300) imageView.fadeIn()
13. More Tricks Lovis Möller @lovisbrot #codetalkshh Write your own extension properties val ViewParent.top
 get() = (this as View).top val patentTop = view.getParent().top
14. But how? Lovis Möller @lovisbrot #codetalkshh Strategies • Whole file or snippet-based
15. But how? Lovis Möller @lovisbrot #codetalkshh Strategies • Whole file or snippet-based • Rewrite from scratch
16. But how? Lovis Möller @lovisbrot #codetalkshh Strategies • Whole file or snippet-based • Rewrite from scratch • Start with tests?
17. But how? Lovis Möller @lovisbrot #codetalkshh Strategies • Whole file or snippet-based • Rewrite from scratch • Start with tests? • Not on Backlog • Whenever you touch a file, convert it • take the chance to improve the design!
18. But how? Lovis Möller @lovisbrot #codetalkshh Strategies • Whole file or snippet-based • Rewrite from scratch • Start with tests? • Not on Backlog • Whenever you touch a file, convert it • take the chance to improve the design! • Don't go overboard
19. But how? Lovis Möller @lovisbrot #codetalkshh Strategies • Whole file or snippet-based • Rewrite from scratch • Start with tests? • Not on Backlog • Whenever you touch a file, convert it • take the chance to improve the design! • Don't go overboard • Keep it simple
20. Thanks a lot! Lovis Möller @lovisbrot #codetalkshh
21. Lovis Möller @lovisbrot #codetalkshh github.com/lmller/codetalks2017 github.com/lmller/gof-in-kotlin @lovisbrot magicline.com/de/karriere Examples meetup.com/Kotlin-User-Group-Hamburg