Using Kotlin in Production

Kotlin has fast become the new hotness in the Android world - but what is the reality of adding it to an app which is rapidly being built for a fast growing startup? In this talk we'll cover how we went about adding Kotlin to the Monzo app, why we made those choices and how it went.

https://devfest.gdg.london/schedule/2017-11-11?sessionId=204

Transcript

1. Using Kotlin in Production @emmaguy
2. How did we get there? Did it go well? Lessons learnt
3. Convince your team
4. Have an offsite Nerd out!
5. Convince your manager(s)
7. Christina Lee @ Google I/O https://www.youtube.com/watch?v=fPzxfeDJDzY
8. Everyone is sold! Let’s go!
9. “Let’s just start using it” - me, March 2017
10. Plan
11. Decide how to use it
12. Only tests? A layer of your application’s architecture? ‘Anything new’?
13. Tests only
14. @Test public void register_noPhoneNumber_showContactSupport() { when(pinManager.fetchPhoneNumber()).thenReturn(""); presenter.register(view); verify(view).showContactSupport(); }
15. @Test fun register_noPhoneNumber_showContactSupport() { whenever(pinManager.fetchPhoneNumber()).thenReturn("") presenter.register(view) verify(view).showContactSupport() }
16. Figure out any potential “incompatibilities” e.g. Realm, Lombok
19. Learn & Adapt
20. Progressed to use in data layer of our app ...then in Activities (replacing ButterKnife) ...then anything new!
21. Expect discussions about nullability
22. #kotlin-tips
23. Stick with what you committed to for a while Assess Make changes
25. Awesome things
26. Kotlin = great for hiring
27. @Deprecated https://hackernoon.com/how-kotlins-deprecated-relieves-pain-of-colossal-refactoring-8577545aaed
28. Extension methods
29. @Override public void showLoading() { progressBar.setVisibility(View.VISIBLE); } or override fun showLoading() { progressBar.visible() }
30. fun ImageView.loadUrl(url: String) { Picasso.with(context).load(url).into(this) } imageView.loadUrl(url)
31. fun Activity.screenWidth(): Int { val metrics = DisplayMetrics() windowManager.defaultDisplay.getMetrics(metrics) return metrics.widthPixels }
32. Named/default arguments
33. fun card( id: String = UUID.randomUUID().toString(), expires: String = "24/20", cardStatus: CardStatus = CardStatus.ACTIVE ): Card { return Card(id, expires, cardStatus) } Card(expires = "03/16", cardStatus = CardStatus.INACTIVE)
34. setUpgradeBannerStyle(true) or setUpgradeBannerStyle(loudStyle = true)
35. apply { }
36. val arguments = Bundle().apply { putString(KEY_ID, id) }
37. Things we learnt
38. “Convert any file you touch” doesn’t work
39. There is no ‘static’
40. companion object {} https://medium.com/@BladeCoder/exploring-kotlins-hidden-costs-part-1-fbb9935d9b62
41. Where do I put constants?
43. Auto convert is not always your friend
45. SAM Conversion
46. public interface PayeeClickListener { void onPayeeClicked(Payee payee); }
47. adapter.setPayeeClickListener(payee -> /* do something */);
48. adapter.setPayeeClickListener(PayeeClickListener { /* do something */ })
49. But, if we convert the interface to Kotlin
50. adapter.setPayeeClickListener(object : PayeeClickListener { override fun onPayeeClicked(payee: Payee) { // do something } })
51. New thing = less mature ecosystem IDE integration, style guide, code coverage tools
52. Would you do it again?
53. Absolutely.
55. Thank you! @emmaguy
56. Questions? @emmaguy