Dependency injection from zero to hero with Koin

Koin (https://insert-koin.io) is a pragmatic dependency injection framework for Kotlin/Android developers. Let's see how it will make your life easier thanks to the power of Kotlin language: from basics to the setup of Android architecture's components, without forgetting the testing part... And of course, how to migrate your “old” Dagger project.

At the menu also, the presentation of the new 2.0 release and some advanced APIs!

(light/online version)

Transcript

1. Dependency injection from zero to hero with Koin Arnaud Giuliani @arnogiu Kotliners 2019
2. The CoffeeMaker App ☕ * aka the thermosiphon dagger’s nightmare sample app
3. Pump +pump() Thermosiphon Heater +off() +on() +isHot() ElectricHeater CoffeeMaker +brew()
4. interface Heater { fun on() fun off() fun isHot() : Boolean }
5. class ElectricHeater : Heater { var heating: Boolean = false override fun on() { println("~ ~ ~ heating ~ ~ ~") heating = true } override fun off() { heating = false } override fun isHot(): Boolean = heating }
6. interface Pump { fun pump() }
7. class Thermosiphon(val heater: Heater) : Pump{ override fun pump() { if (heater.isHot()){ println("=> => pumping => =>") } } }
8. class CoffeeMaker(val pump: Pump, val heater: Heater) { fun brew() { heater.on() pump.pump() println(" [_]P coffee! [_]P ") heater.off() } }
9. class CoffeeApp { val coffeeMaker: CoffeeMaker fun run() { coffeeMaker.brew() } } fun main(vararg args: String) { startKoin(listOf(coffeeMakerModule)) CoffeeApp().run() }
10. Pump +pump() Thermosiphon Heater +off() +on() +isHot() ElectricHeater CoffeeMaker +brew() how to assemble it?
11. Koin
12. - Intuitive DSL to describe it - Lightweight container to run it - Simple API to use it
13. repositories { jcenter() } dependencies { // Koin for Kotlin implementation ‘org.koin:koin-core:$version’ } Gradle Setup
14. class ElectricHeater : Heater class Thermosiphon(val heater: Heater) : Pump class CoffeeMaker(val pump: Pump, val heater: Heater) val coffeeMakerModule = module { single { CoffeeMaker(get(),get()) } single<Pump>{ Thermosiphon(get()) } single<Heater> { ElectricHeater() } } * also multi modules
15. class ElectricHeater : Heater class Thermosiphon(val heater: Heater) : Pump class CoffeeMaker(val pump: Pump, val heater: Heater) val coffeeMaker = module { single { CoffeeMaker(get(),get()) } } val coffeeStuffs = module { single<Pump>{ Thermosiphon(get()) } single<Heater> { ElectricHeater() } } * also multi modules
16. Koin Component a class that can use the Koin container
17. ✅ open access to Kotlin extensions: inject(), get() identify a class linked to the Koin API KoinComponent is an interface marker bootstrap & help integrate with runtime (Android…)
18. class CoffeeApp : KoinComponent { val coffeeMaker: CoffeeMaker by inject() fun run() { coffeeMaker.brew() } } fun main(vararg args: String) { startKoin(listOf(coffeeMakerModule)) CoffeeApp().run() }
19. startKoin to start the Koin container
20. fun run() { coffeeMaker.brew() } } fun main(vararg args: String) { startKoin { modules(coffeeMakerModule) } CoffeeApp().run() }
21. ~ ~ ~ heating ~ ~ ~ => => pumping => => [_]P coffee! [_]P
22. Pump +pump() Thermosiphon Heater +off() +on() +isHot() ElectricHeater CoffeeMaker +brew() lazy!
23. val coffeeMakerModule = module { single { CoffeeMaker(get(),lazy { get<Heater() }) } single<Pump>{ Thermosiphon(get()) } single<Heater> { ElectricHeater() } }
24. class CoffeeMaker(private val pump: Pump, _heater: Lazy<Heater>) { val heater by _heater fun brew() { heater.on() pump.pump() println(" [_]P coffee! [_]P ") heater.off() } } * Lazy is a Kotlin type
25. Let’s get back with Dagger ...
26. @Module(includes = [(PumpModule::class)]) internal class DripCoffeeModule { @Provides @Singleton fun provideHeater(): Heater { return ElectricHeater() } }
27. @Module abstract class PumpModule { @Binds abstract fun providePump(pump: Thermosiphon): Pump }
28. @Singleton @Component(modules = [DripCoffeeModule::class]) interface CoffeeApp { fun maker(): CoffeeMaker }
29. class Thermosiphon @Inject constructor(private val heater: Heater) : Pump{ override fun pump() { if (heater.isHot()){ println("=> => pumping => =>") } } }
30. class CoffeeMaker @Inject constructor(private val pump: Pump, private val _heater: Lazy<Heater>) { val heater by lazy { _heater.get() } fun brew() { heater.on() pump.pump() println(" [_]P coffee! [_]P ") heater.off() } } * Lazy is a Dagger type
31. Just migrate to Koin, what else?
32. Pump +pump() Thermosiphon Heater +off() +on() +isHot() ElectricHeater CoffeeMaker +brew()
33. val coffeeMakerModule = module { single<Heater> { ElectricHeater() } }
34. class Thermosiphon @Inject constructor(private val heater: Heater) : Pump{ override fun pump() { if (heater.isHot()){ println("=> => pumping => =>") } } }
35. class Thermosiphon : Pump, KoinComponent { private val heater: Heater by inject() override fun pump() { if (heater.isHot()){ println("=> => pumping => =>") } } }
36. class CoffeeMaker @Inject constructor(private val pump: Pump, private val _heater: Lazy<Heater>) { val heater: Heater by lazy { _heater.get() } fun brew() { heater.on() pump.pump() println(" [_]P coffee! [_]P ") heater.off() } }
37. class CoffeeMaker @Inject constructor(private val pump: Pump) : KoinComponent val heater: Heater by inject() fun brew() { heater.on() pump.pump() println(" [_]P coffee! [_]P ") heater.off() } }
38. http://bit.ly/dagger2koin From Dagger to Koin, a step by step migration guide
40. Can’t create Android components directly
41. Activity, Fragment, Service … are extended as KoinComponent! out of the box! ✅ Koin extensions for Android
42. repositories { jcenter() } dependencies { // Koin for Android implementation ‘org.koin:koin-android:$version’ } Gradle Setup
43. class MyApplication : Application() { override fun onCreate() { super.onCreate() // Reference Android context in Koin startKoin { androidLogger() androidContext(this@MyApplication) modules(coffeeMakerModule) } } }
44. class MyActivity : AppCompatActivity() { val coffeeMaker: CoffeeMaker by inject() }
45. Get the Android context?
46. class MyComponent(val context : Context) val myModule = module { single { MyComponent(androidContext()) } }
47. class MyComponent(val context : Context) val myModule = module { single { MyComponent(get()) } }
48. Dealing with transient components? ie. presenters …
49. class MyPresenter val myModule = module { // will create MyPresenter on each call factory { MyPresenter() } } class MyActivity : AppCompatActivity() { }
50. class MyPresenter val myModule = module { // will create MyPresenter on each call factory { MyPresenter() } } class MyActivity : AppCompatActivity() { // new instance on each call val presenter: MyPresenter by inject() }
51. Ready for Android Architecture Components
52. repositories { jcenter() } dependencies { // Koin for Android + ViewModel features implementation ‘org.koin:koin-android-viewmodel:$version’ } Gradle Setup
53. ✅ Koin extensions for Android ViewModel
54. class MyViewModel(val coffeeMaker : CoffeeMaker) : ViewModel() val coffeeMakerModule = module { viewModel { MyViewModel(get()) } } class MyActivity : AppCompatActivity() { // inject ViewModel val myViewModel: MyViewModel by viewModel() override fun onCreate(savedInstanceState: Bundle?) { // get ViewModel val myViewModel: MyViewModel = getViewModel() }
55. //... viewModel { MyViewModel(get()) } } class MyActivity : AppCompatActivity() { // inject ViewModel val myViewModel: MyViewModel by viewModel() override fun onCreate(savedInstanceState: Bundle?) { // get ViewModel val myViewModel: MyViewModel = getViewModel() }
56. //... viewModel { MyViewModel(get()) } } class MyFragment : Fragment() { // inject ViewModel val myViewModel: MyViewModel by viewModel() override fun onCreate(savedInstanceState: Bundle?) { // get ViewModel val myViewModel: MyViewModel = getViewModel() }
57. //... viewModel { MyViewModel(get()) } } class MyFragment : Fragment() { // inject ViewModel from parent activity val myViewModel: MyViewModel by sharedViewModel() overrid e fun onCreate(savedInstanceState: Bundle?) { // get ViewModel val myViewModel: MyViewModel = getViewModel() }
58. //... viewModel { MyViewModel(get()) } } class MyFragment : Fragment() { // inject ViewModel from parent activity val myViewModel: MyViewModel by sharedViewModel() overrid e fun onCreate(savedInstanceState: Bundle?) { // get ViewModel val myViewModel: MyViewModel = getViewModel() } val viewModel = ViewModelProviders .of(this.activity) .get(MyViewModel::class.java)
59. Testing easily with Koin ✅
60. repositories { jcenter() } dependencies { // Koin for Tests testImplementation ‘org.koin:koin-test:$version’ } Gradle Setup
61. Checking your modules ✔
62. class ModuleTest { @Test fun `check all definitions from coffeeMakerModule`() { startKoin { modules(coffeeMakerModule) }.checkModules() } }
63. ✅ Koin extensions with JUnit & Mockito
64. class CoffeeMakerTest : KoinTest { val coffeeMaker: CoffeeMaker by inject() val heater: Heater by inject() @Test fun testHeaterIsTurnedOnAndThenOff() { startKoin { modules(coffeeMakerModule) } declareMock<Heater>() given(heater.isHot()).will { true } coffeeMaker.brew() Mockito.verify(heater, times(1)).on() Mockito.verify(heater, times(1)).off() } }
65. class CoffeeMakerTest : KoinTest { val coffeeMaker: CoffeeMaker by inject() val heater: Heater by inject() @Test fun testHeaterIsTurnedOnAndThenOff() { startKoin { modules(coffeeMakerModule) } declareMock<Heater>() given(heater.isHot()).will { true } coffeeMaker.brew() Mockito.verify(heater, times(1)).on() Mockito.verify(heater, times(1)).off() } }
66. class CoffeeMakerTest : KoinTest { val coffeeMaker: CoffeeMaker by inject() val heater: Heater by inject() @Test fun testHeaterIsTurnedOnAndThenOff() { startKoin { modules(coffeeMakerModule) } declareMock<Heater>() given(heater.isHot()).will { true } coffeeMaker.brew() verify(heater, times(1)).on() verify(heater, times(1)).off() } }
67. Upgrading to Koin 2.0
68. Since first 1.0 version…
69. Simple DSL module, single, factory, get
70. Pragmatic API ✌ KoinComponent, get, inject
71. ⚠ performances ⚠
72. @Sloydev - 450 definitions benchmark
75. * non linear startup / Kotlin overhead ** split modules startup if needed
76. Benchmarks https://github.com/InsertKoinIO/thermosiphon_dagger2koin https://github.com/Sloy/android-dependency-injection-performance https://github.com/arnaudgiuliani/android-dependency-injection-performance
77. Upgrade to Koin 2.0
81. Some API Break - Simplified module DSL (no more inner modules) - Revamped Scope API - Context isolation & startKoin DSL (koinApplication) - Definition resolution (default & qualifiers)
82. http://bit.ly/ready4koin
83. More about Koin✨
84. - Container DSL - Qualifiers (string/type) - Global vs isolated context - Scope API - Android, Scopes & lifecycle - Injection Parameters - AndroidX - Koin for Java - Koin for Ktor
85. What is a scope? A scope is a context with fixed duration of time, in which an object exists. When the scope ends, any objects bound under that scope cannot be injected again.
86. Components’ lifetime Container Single Factory Scope Factory Factory
87. Components Container Data Repository View User Session View View
88. module { scope(named("Session")) { scoped { SessionData() } } } // create scope with id "session1" and qualifier "Session" val session1 = getKoin().createScope("session1",named("Session")) // get SessionData instance from scope "session1" val data : SessionData = session1.get() // close instances scope "session1" scope.close()
89. module { scope(named("Session")) { scoped { SessionData() } } } // create scope with id "session1" and qualifier "Session" val session1 = getKoin().createScope("session1",named("Session")) // get SessionData instance from scope "session1" val data : SessionData = session1.get() // close instances scope "session1" session1.close()
90. repositories { jcenter() } dependencies { // Koin for Android + Scope feature implementation ‘org.koin:koin-android-scope:$version’ } Gradle Setup
91. ✅ Extensions for Android Lifecycle + Koin Scope
92. module { scope(named<MyActivity>()) { scoped { MyPresenter() } } } class MyActivity : AppCompatActivity { val presenter : MyPresenter by currentScope.inject() } ** follow lifecycle * currentScope is provided by extension
93. version = “2.0.1" repositories { jcenter() } dependencies { // Kotlin Core features implementation "org.koin:koin-core:$version" // Android basic features implementation "org.koin:koin-android:$version" // Android basic + scope features implementation "org.koin:koin-android-scope:$version" // Android basic + scope + viewmodel features
94. dependencies { // Kotlin Core features implementation "org.koin:koin-core:$version" // Android basic features implementation "org.koin:koin-android:$version" // Android basic + scope features implementation "org.koin:koin-android-scope:$version" // Android basic + scope + viewmodel features implementation "org.koin:koin-android-viewmodel:$version" // Kotlin Checks + JUnit & Mock features testImplementation "org.koin:koin-test:$version" }
95. dependencies { // Kotlin Core features implementation "org.koin:koin-core:$version" // Android basic features implementation "org.koin:koin-android:$version" // Android basic + scope features implementation "org.koin:koin-android-scope:$version" // Android basic + scope + viewmodel features implementation "org.koin:koin-android-viewmodel:$version" // Kotlin Checks + JUnit & Mock features testImplementation "org.koin:koin-test:$version" }
96. dependencies { // Kotlin Core features implementation "org.koin:koin-core:$version" // Android basic features implementation "org.koin:koin-android:$version" // Android basic + scope features implementation "org.koin:koin-android-scope:$version" // Android basic + scope + viewmodel features implementation "org.koin:koin-android-viewmodel:$version" // Kotlin Checks + JUnit & Mock features testImplementation "org.koin:koin-test:$version" }
97. dependencies { // Kotlin Core features implementation "org.koin:koin-core:$version" // Android basic features implementation "org.koin:koin-android:$version" // Android basic + scope features implementation "org.koin:koin-android-scope:$version" // Android basic + scope + viewmodel features implementation "org.koin:koin-android-viewmodel:$version" // Kotlin Checks + JUnit & Mock features testImplementation "org.koin:koin-test:$version" }
98. dependencies { // Kotlin Core features implementation "org.koin:koin-core:$version" // Android basic features implementation "org.koin:koin-android:$version" // Android basic + scope features implementation "org.koin:koin-android-scope:$version" // Android basic + scope + viewmodel features implementation "org.koin:koin-android-viewmodel:$version" // Kotlin Checks + JUnit & Mock features testImplementation "org.koin:koin-test:$version" }
99. Before starting with Koin…
100. Try the getting started projects * look at code samples
102. Read the quick references
103. Add it step by step to your project * start with small components
104. Check your modules
105. Review your software design
106. Keep it simple
107. Documentation reference for deeper look * or even in source code
109. and …
110. StackOverflow, Github & Slack for any question
112. @insertkoin_io koin-developers
113. Thanks! Early adopters, Community feedback, Conference, talks, meetups…
114. Spread the word!
115. insert-koin.io
116. Arnaud Giuliani - @arnogiu Thank you!