Live Coding: Simon Says Game in Kotlin

"Where do I start?" How many times have you asked yourself this when you are about to add a new functionality to your project?
Developers deal with daily decision problems that affect huge code bases and little time to come with solutions.
In this talk we will build the famous Simon Says game for Android to show how we can come up with a solution parting from requirements that are turned into very specific test cases.
Along the way we will see the advantages that Kotlin provides us and a small sample of the power that Arrow can add to your Android project incorporating functional programming.

Transcript

1. Live Coding: Simon Says Game In Kotlin Rocío Ortega @Perrankana
2. • Memory Skill game • Invented by Ralph H. Baer and Howard J Morrison in 1978. Some things about Simon Says Photo by Debaird: https://www.flickr.com/photos/debaird Simon Says Game - Android
3. • Start Game! • 4 colours • Colour sequences Our Simon Says Version Photo by Debaird: https://www.flickr.com/photos/debaird Simon Says Game - Android
4. Start point Simon Says Game - Android
5. Start point Data Simon Says Game - Android
6. Start point ColorSequenceRepository Data Simon Says Game - Android
7. Start point ColorSequenceDataSource ColorSequenceRepository Data Simon Says Game - Android
8. Start point ColorSequenceDataSource ColorProvider ColorSequenceRepository Data Simon Says Game - Android
9. Start point ColorSequenceRepository PositionRepository Data Simon Says Game - Android
10. Start point ColorSequenceRepository PositionRepository PositionDataSource Data Simon Says Game - Android
11. Start point ColorSequenceRepository PositionRepository Data Domain Simon Says Game - Android
12. Start point StartGameUseCase ColorSequenceRepository PositionRepository Data Domain Simon Says Game - Android
13. Start point StartGameUseCase ColorSequenceRepository PositionRepository ValidateColorUseCase Data Domain Simon Says Game - Android
14. Data Domain StartGameUseCase ColorSequenceRepository PositionRepository ValidateColorUseCase Presentation Start point Simon Says Game - Android
15. Data Domain StartGameUseCase ColorSequenceRepository PositionRepository ValidateColorUseCase Presentation Start point GamePresenter Simon Says Game - Android
16. Data Domain StartGameUseCase ColorSequenceRepository PositionRepository ValidateColorUseCase Presentation Start point GamePresenter GameFragment / View Simon Says Game - Android
17. Data Domain StartGameUseCase ColorSequenceRepository PositionRepository Presentation What we will do? GamePresenter GameFragment / View ValidateColorUseCase Simon Says Game - Android
18. JUnit4 Mockito Unit Test Simon Says Game - Android
19. Coroutines The Kotlin team defines coroutines as “lightweight threads”. They are sort of tasks that the actual threads can execute. Simon Says Game - Android
20. CoroutineScope public interface CoroutineScope { public val coroutineContext: CoroutineContext } Coroutines Simon Says Game - Android
21. CoroutineContext coroutineContext = (job + Dispatchers.Main) Coroutines Simon Says Game - Android
22. Launch public fun CoroutineScope.launch( context: CoroutineContext = EmptyCoroutineContext, start: CoroutineStart = CoroutineStart.DEFAULT, block: suspend CoroutineScope.() -> Unit ): Job Coroutines Simon Says Game - Android
23. withContext public suspend fun <T> withContext( context: CoroutineContext, block: suspend CoroutineScope.() -> T ): T Coroutines Simon Says Game - Android
24. class GamePresenter() : CoroutineScope by MainScope() { fun onDetach() { cancel() } } Coroutines Simon Says Game - Android
25. class GamePresenter() : CoroutineScope by MainScope() { fun onDetach() { cancel() } } @Suppress("FunctionName") public fun MainScope(): CoroutineScope = ContextScope(SupervisorJob() + Dispatchers.Main) Coroutines Simon Says Game - Android
26. class GamePresenter() : CoroutineScope by MainScope() { fun onDummyFunction() { launch { val result = withContext(Dispatcher.IO) { doTakingLotOfTime() } doThingsInMainWith(result) } } } Coroutines Simon Says Game - Android
27. A cold asynchronous data stream that sequentially emits values and completes normally or with an exception. Flow flow { colorSequence.forEach { value -> delay(delayTime) emit(value) } } Simon Says Game - Android
28. Functional with Λrrow Simon Says Game - Android
29. Functional with Λrrow Simon Says Game - Android DataTypes
30. Try<A> Functional with Λrrow DataTypes Simon Says Game - Android
31. Functional with Λrrow DataTypes Simon Says Game - Android Try<A>
32. Functional with Λrrow Option<A> Try<A> DataTypes Simon Says Game - Android
33. Functional with Λrrow Option<A> Try<A> DataTypes Simon Says Game - Android data class Some<out A>(val a: A) : Option<T>() { override fun isEmpty() = false override fun toString(): String = “Some($a)" }
34. Functional with Λrrow Option<A> Try<A> DataTypes Simon Says Game - Android data class Some<out T>(val t: T) : Option<T>() { override fun isEmpty() = false override fun toString(): String = "Some($t)" } object None : Option<Nothing>() { override fun isEmpty() = true override fun toString(): String = "None" }
35. Validated<A,B> Functional with Λrrow Option<A> Try<A> DataTypes Simon Says Game - Android
36. Validated<A,B> Functional with Λrrow Option<A> Try<A> DataTypes Simon Says Game - Android data class Valid<out B>(val b: B) : Validated<Nothing, B>()
37. Validated<A,B> Functional with Λrrow Option<A> Try<A> DataTypes Simon Says Game - Android data class Valid<out B>(val b: B) : Validated<Nothing, B>() data class Invalid<out A>(val a: A) : Validated<A, Nothing>()
38. Functional with Λrrow Option<A> Try<A> DataTypes Validated<A,B> Simon Says Game - Android
39. Fold Functional with Λrrow Option<A> Try<A> DataTypes Validated<A,B> Simon Says Game - Android
40. Fold Functional with Λrrow Option<A> Try<A> DataTypes Validated<A,B> Simon Says Game - Android inline fun <R> fold(ifEmpty: () -> R, ifSome: (A) -> R): R = when (this) { is None -> ifEmpty() is Some<A> -> ifSome(t) }
41. Fold Functional with Λrrow Option<A> Try<A> DataTypes Validated<A,B> Simon Says Game - Android inline fun <B> fold(fe: (E) -> B, fa: (A) -> B): B = when (this) { is Valid -> fa(a) is Invalid -> (fe(e)) }
42. Fold fold({ /*failed block*/ },{ /*succeed block*/ }) Functional with Λrrow Option<A> Try<A> DataTypes Validated<A,B> Simon Says Game - Android
43. There are more solutions for the same problem. Disclaimer Simon Says Game - Android
44. Simon Says Game - Android 44 Let’s rock!
45. Conclusion Simon Says Game - Android
46. Conclusion • Requirements into UnitTests Simon Says Game - Android
47. Conclusion • Requirements into UnitTests • Coroutines in GamePresenter Simon Says Game - Android
48. Conclusion • Requirements into UnitTests • Coroutines in GamePresenter • Flow to emit Colors in Sequence Simon Says Game - Android
49. Conclusion • Requirements into UnitTests • Coroutines in GamePresenter • Flow to emit Colors in Sequence • Arrow datatypes Simon Says Game - Android
50. • Requirements into UnitTests • Coroutines in GamePresenter • Flow to emit Colors in Sequence • Arrow datatypes Conclusion Simon Says Game - Android
51. https://github.com/perrankana/simonSays Rocío Ortega @Perrankana Simon Says Game - Android