Architecture Patterns in Practice with Kotlin

Kotlin is here and some Architecture Patterns need to be adapted.

From Karumi we've dedicated last 3 years talking about architecture and design patterns, each solution has pros and cons and could be good for different problems and kind of applications.

Kotlin brings to us different tools and ways to write code these can help us to write different patterns or apply different technics to that patterns.

In this talk, we present some commons problems in app designs and how we can provide solutions in Kotlin.

Transcript

1. Architecture Patterns in Practice with Kotlin Jorge Juan Barroso Carmona Developer and GDE jorge@karumi.com @flipper83
2. Testing for android & iOS. Trainings Architecture, Patterns and principles for Android & iOS. Mastering Git. Advanced mobile development. Testing for android & iOS. Architecture, Patterns and principles for Android & iOS. Companies For Everybody
3. Sergio Gutierrez Senior Full Stack Engineer Pedro Gomez Senior Full Stack Engineer Davide Mendolia Senior Full Stack Engineer Fran Toro Senior Mobile Engineer
4. Adam Tornhill “Computer languages differ not so much in what they make possible, but in what they make easy.” Larry Wall
5. https://github.com/Karumi/SuperHeroesKotlin
7. Why
8. Write readable code
9. Testable
10. Remove boilerplate code
11. Easy to change and evolve
12. Kotlin to avoid Java problems
13. Activity Fragment Service View … Presenter View Use Case Rich Model Repository DataSource Api Retrofit SharedPref Api Sync Execution
14. Android is a framework based on inheritance
15. Activity Fragment Service View … Presenter View Domain Model Presentation Model Use Case
16. Adam Tornhill class MainActivity : BaseActivity(), SuperHeroesPresenter.View { override val presenter: SuperHeroesPresenter by injector.instance() private lateinit var adapter: SuperHeroesAdapter override val layoutId: Int = R.layout.main_activity override val toolbarView: Toolbar get() = toolbar /*…*/ }
17. Adam Tornhill class MainActivity : BaseActivity(), SuperHeroesPresenter.View { override val presenter: SuperHeroesPresenter by injector.instance() private lateinit var adapter: SuperHeroesAdapter override val layoutId: Int = R.layout.main_activity override val toolbarView: Toolbar get() = toolbar /*…*/ } Computed properties
18. Adam Tornhill abstract class BaseActivity : KodeinAppCompatActivity(), LifecyclePublisher by lifeCycleLinker { abstract val layoutId: Int abstract val presenter: LifecycleSubscriber abstract val toolbarView: Toolbar abstract val activityModules: Module /*…*/ }
19. Adam Tornhill class MainActivity : BaseActivity(), SuperHeroesPresenter.View { override val presenter: SuperHeroesPresenter by injector.instance() private lateinit var adapter: SuperHeroesAdapter override val layoutId: Int = R.layout.main_activity override val toolbarView: Toolbar get() = toolbar /*…*/ } override properties
20. Adam Tornhill class MainActivity : BaseActivity(), SuperHeroesPresenter.View { override val presenter: SuperHeroesPresenter by injector.instance() private lateinit var adapter: SuperHeroesAdapter override val layoutId: Int = R.layout.main_activity override val toolbarView: Toolbar get() = toolbar /*…*/ }
21. Adam Tornhill abstract class BaseActivity : KodeinAppCompatActivity(), LifecyclePublisher by lifeCycleLinker { abstract val layoutId: Int abstract val presenter: LifecycleSubscriber abstract val toolbarView: Toolbar abstract val activityModules: Module /*…*/ } Delegate
22. Adam Tornhill abstract class BaseActivity : KodeinAppCompatActivity(), LifecyclePublisher by lifeCycleLinker { abstract val presenter: LifecycleSubscriber /*…*/ override fun onResume() { super.onResume() update() } override fun onDestroy() { unregister(presenter) super.onDestroy() } delegate to..
23. LifecycleLinker : LifecyclePublisher private val receivers = ArrayList<LifecycleSubscriber>() override fun unregister (subscriber: LifecycleSubscriber) { receivers.remove(subscriber) } override fun update() { receivers .forEach (LifecycleSubscriber::update) } /*…*/ } Adam Tornhill override fun onResume() { super.onResume() update() } override fun onDestroy() { unregister(presenter) super.onDestroy() } BaseActivity : LifecyclePublisher by lifeCycleLinker
24. Avoid memory leaks
25. Big problem using passive Views on presenters
26. Activity Fragment Service View … Presenter View Domain Model Presentation Model Use Case
27. Adam Tornhill class SuperHeroesPresenter( view: View, private val getSuperHeroes: GetSuperHeroes) :LifecycleSubscriber { private val view: View? by weak(view) /*…*/ }
28. Adam Tornhill class SuperHeroesPresenter( view: View, private val getSuperHeroes: GetSuperHeroes) :LifecycleSubscriber { private val view: View? by weak(view) /*…*/ } argument properties
29. Adam Tornhill class SuperHeroesPresenter( view: View, private val getSuperHeroes: GetSuperHeroes) :LifecycleSubscriber { private val view: View? by weak(view) /*…*/ } argument properties delegate property
30. fun <T> weak(value: T) = WeakRef(value) class WeakRef<out T>(value: T) { private val weakReference: WeakReference<T> = WeakReference(value) operator fun getValue(thisRef: Any, property: KProperty<*>): T? = weakReference.get() } Adam Tornhill class SuperHeroesPresenter( view: View, private val getSuperHeroes: GetSuperHeroes) :LifecycleSubscriber { private val view: View? by weak(view) /*…*/ } argument poperties
31. fun <T> weak(value: T) = WeakRef(value) class WeakRef<out T>(value: T) { private val weakReference: WeakReference<T> = WeakReference(value) operator fun getValue(thisRef: Any, property: KProperty<*>): T? = weakReference.get() } Adam Tornhill class SuperHeroesPresenter( view: View, private val getSuperHeroes: GetSuperHeroes) :LifecycleSubscriber { private val view: View? by weak(view) /*…*/ }
32. class SuperHeroesPresenter( view: View, private val getSuperHeroes: GetSuperHeroes) : LifecycleSubscriber { private val view: View? by weak(view) override fun update() { view?.showLoading() refreshSuperHeroes() } We’re acting (Optional)
33. fun <T> weak(value: T) = WeakRef(value) class WeakRef<out T>(value: T) { private val weakReference: WeakReference<T> = WeakReference(value) operator fun getValue(thisRef: Any, property: KProperty<*>): T? = weakReference.get() } Adam Tornhill class SuperHeroesPresenter( view: View, private val getSuperHeroes: GetSuperHeroes) :LifecycleSubscriber { private val view: View? by weak(view) /*…*/ }
34. Working with Errors
35. Only one code path
36. Either Monad
37. A monad is just a monoid in the category of endofunctors
39. Either<Left, Right>
40. Either<Left, Right> Error Success
41. class NetworkSuperHeroDataSource( private val apiClient: CharacterApiClient) : SuperHeroDataSource { override fun get(key: String): Either<DomainError, SuperHero> = try { mapResponse(apiClient.getCharacter(key)) { mapSuperHero(it) } } catch (exception: Exception) { Either.left(mapException(exception)) } /*…*/ } Adam Tornhill
42. class NetworkSuperHeroDataSource( private val apiClient: CharacterApiClient) : SuperHeroDataSource { override fun get(key: String): Either<DomainError, SuperHero> = try { mapResponse(apiClient.getCharacter(key)) { mapSuperHero(it) } } catch (exception: Exception) { Either.left(mapException(exception)) } /*…*/ } Adam Tornhill
43. class NetworkSuperHeroDataSource( private val apiClient: CharacterApiClient) : SuperHeroDataSource { override fun get(key: String): Either<DomainError, SuperHero> = try { mapResponse(apiClient.getCharacter(key)) { mapSuperHero(it) } } catch (exception: Exception) { Either.left(mapException(exception)) } /*…*/ } Adam Tornhill
44. GetSuperHeroes: fun invoke(): Either<DomainError, List<SuperHero>> SuperHeroesRepository: fun getAllSuperHeroes(): Either<DomainError, List<SuperHero>> SuperHeroDataSource: fun getAll(): Either<DomainError, List<SuperHero>> Adam Tornhill
45. GetSuperHeroes: fun invoke(): Either<DomainError, List<SuperHero>> SuperHeroesRepository: fun getAllSuperHeroes(): Either<DomainError, List<SuperHero>> SuperHeroDataSource: fun getAll(): Either<DomainError, List<SuperHero>> Adam Tornhill Don’t break the chain
46. private fun refreshSuperHeroes() = async { val result = await { getSuperHeroes() } view?.hideLoading() when (result) { is Right -> showSuperHeroes(result.r) is Left -> view?.showError(result.l) } } Adam Tornhill MainPresenter: switch on steroids
47. private fun refreshSuperHeroes() = async { val result = await { getSuperHeroes() } view?.hideLoading() when (result) { is Right -> showSuperHeroes(result.r) is Left -> view?.showError(result.l) } } Adam Tornhill MainPresenter: smart cast
48. abstract class BaseActivity : KodeinAppCompatActivity(), LifecyclePublisher by lifeCycleLinker { /*…*/ fun showError(error: DomainError) = Snackbar.make(toolbarView, error.asString(this), Snackbar.LENGTH_LONG).show() } Adam Tornhill
49. abstract class BaseActivity : KodeinAppCompatActivity(), LifecyclePublisher by lifeCycleLinker { /*…*/ fun showError(error: DomainError) = Snackbar.make(toolbarView, error.asString(this), Snackbar.LENGTH_LONG).show() } Adam Tornhill
50. fun DomainError.asString(context: Context): String = context.getString(getMessage(this)) fun getMessage(domainError: DomainError): Int = when (domainError) { is NotInternetDomainError -> R.string.error_not_internet_message is NotIndexFoundDomainError -> R.string.error_superhero_not_found_message is AuthDomainError -> R.string.error_invalid_credentials is UnknownDomainError -> R.string.error_unknown_message } Adam Tornhill extension method
51. fun DomainError.asString(context: Context): String = context.getString(getMessage(this)) fun getMessage(domainError: DomainError): Int = when (domainError) { is NotInternetDomainError -> R.string.error_not_internet_message is NotIndexFoundDomainError -> R.string.error_superhero_not_found_message is AuthDomainError -> R.string.error_invalid_credentials is UnknownDomainError -> R.string.error_unknown_message } Adam Tornhill
52. fun DomainError.asString(context: Context): String = context.getString(getMessage(this)) fun getMessage(domainError: DomainError): Int = when (domainError) { is NotInternetDomainError -> R.string.error_not_internet_message is NotIndexFoundDomainError -> R.string.error_superhero_not_found_message is AuthDomainError -> R.string.error_invalid_credentials is UnknownDomainError -> R.string.error_unknown_message } Adam Tornhill Compile error!!
53. sealed class DomainError object NotInternetDomainError : DomainError() data class UnknownDomainError( val errorMessage: String = "Unknown Error") : DomainError() data class NotIndexFoundDomainError(val key: String) : DomainError() object AuthDomainError : DomainError() Adam Tornhill
54. make code readable
55. Kotlin can increase your readability
56. improve command pattern
57. class SuperHeroesPresenter( view: View, private val getSuperHeroes: GetSuperHeroes) : LifecycleSubscriber { private fun refreshSuperHeroes() = async { val result = await { getSuperHeroes() } view?.hideLoading() when (result) { is Right -> showSuperHeroes(result.r) is Left -> view?.showError(result.l) } } /*…*/ } Adam Tornhill is this a method? or is an object?
58. class GetSuperHeroes( private val superHeroesRepository: SuperHeroRepository) { operator fun invoke(): Either<DomainError, List<SuperHero>> = superHeroesRepository .getAllSuperHeroes() } Adam Tornhill Override operators getSuperHeroes()
59. improve domain models
60. data class SuperHero( val id: String, val name: String, val photo: String? = null, val isAvenger: Boolean, val description: String) Adam Tornhill
61. data class SuperHero( val id: String, val name: String, val photo: String? = null, val isAvenger: Boolean, val description: String) Adam Tornhill All domain models in the same file
62. Concurrency problems
63. Activity Fragment Service View … Presenter View Use Case Rich Model Repository DataSource Api Retrofit SharedPref Api Sync Execution
64. Coroutines for all
65. class SuperHeroesPresenter( view: View, private val getSuperHeroes: GetSuperHeroes) : LifecycleSubscriber { private fun refreshSuperHeroes() = async { val result = await { getSuperHeroes() } view?.hideLoading() when (result) { is Right -> showSuperHeroes(result.r) is Left -> view?.showError(result.l) } } /*…*/ }
66. class SuperHeroesPresenter( view: View, private val getSuperHeroes: GetSuperHeroes) : LifecycleSubscriber { private fun refreshSuperHeroes() = async { val result = await { getSuperHeroes() } view?.hideLoading() when (result) { is Right -> showSuperHeroes(result.r) is Left -> view?.showError(result.l) } } /*…*/ }
67. class SuperHeroesPresenter( view: View, private val getSuperHeroes: GetSuperHeroes) : LifecycleSubscriber { private fun refreshSuperHeroes() = async { val result = await { getSuperHeroes() } view?.hideLoading() when (result) { is Right -> showSuperHeroes(result.r) is Left -> view?.showError(result.l) } } /*…*/ }
68. Dependency injection
69. Dagger 2 vs Kodein
70. class MainActivity : BaseActivity(), SuperHeroesPresenter.View { override val presenter: SuperHeroesPresenter by injector.instance() /*...*/ override val activityModules = Module(allowSilentOverride = true) { bind<SuperHeroesPresenter>() with provider { SuperHeroesPresenter(this@MainActivity, instance()) } bind<GetSuperHeroes>() with provider{ GetSuperHeroes(instance()) } }
71. class MainActivity : BaseActivity(), SuperHeroesPresenter.View { override val presenter: SuperHeroesPresenter by injector.instance() /*...*/ override val activityModules = Module(allowSilentOverride = true) { bind<SuperHeroesPresenter>() with provider { SuperHeroesPresenter(this@MainActivity, instance()) } bind<GetSuperHeroes>() with provider{ GetSuperHeroes(instance()) } }
72. class MainActivity : BaseActivity(), SuperHeroesPresenter.View { override val presenter: SuperHeroesPresenter by injector.instance() /*...*/ override val activityModules = Module(allowSilentOverride = true) { bind<SuperHeroesPresenter>() with provider { SuperHeroesPresenter(this@MainActivity, instance()) } bind<GetSuperHeroes>() with provider{ GetSuperHeroes(instance()) } }
73. class MainActivity : BaseActivity(), SuperHeroesPresenter.View { override val presenter: SuperHeroesPresenter by injector.instance() /*...*/ override val activityModules = Module(allowSilentOverride = true) { bind<SuperHeroesPresenter>() with provider { SuperHeroesPresenter(this@MainActivity, instance()) } bind<GetSuperHeroes>() with provider{ GetSuperHeroes(instance()) } }
74. Bibliography They’re the cracks! Clean Code. Uncle Bob. 2008 Kotlin For Android Developers. Antonio Leiva. 2015 GitHub AsyncAwait . metalabdesign. Github funKTionale. MarioAriasC. Kodein. Salomon Brys. Karumi Blog and Katas on github.
75. Find me I am very social! jorge@karumi.com @flipper83 Questions?