Dependency Injection for Kotlin Apps with Koin

Transcript

1. Dependency injection for Kotlin apps with Koin Arnaud Giuliani @arnogiu

2. ! Freelance Software Eng " Mobile First Lead of Koin

   project Arnaud GIULIANI

3. Why a new dependency injection framework?

4. The CoffeeMaker App ☕ * aka the thermosiphon dagger’s nightmare

   sample app

5. Pump +pump() Thermosiphon Heater +off() +on() +isHot() ElectricHeater CoffeeMaker +brew()

6. The Heater

7. interface Heater { fun on() fun off() fun isHot() :

   Boolean }

8. class ElectricHeater : Heater { var heating: Boolean = false

   override fun on() { println("~ ~ ~ heating ~ ~ ~") heating = true } override fun off() { heating = false } override fun isHot(): Boolean = heating }

9. The Thermosiphon

10. interface Pump { fun pump() }

11. class Thermosiphon(val heater: Heater) : Pump{ override fun pump() {

    if (heater.isHot()){ println("=> => pumping => =>") } } }

12. The CoffeeMaker

13. class CoffeeMaker(val pump: Pump, val heater: Heater) { fun brew()

    { heater.on() pump.pump() println(" [_]P coffee! [_]P ") heater.off() } }

14. The CoffeeApp

15. class CoffeeApp { val coffeeMaker: CoffeeMaker fun run() { coffeeMaker.brew()

    } }

16. Pump +pump() Thermosiphon Heater +off() +on() +isHot() ElectricHeater CoffeeMaker +brew()

    how to assemble it?

17. class ElectricHeater : Heater class Thermosiphon(val heater: Heater) : Pump

    class CoffeeMaker(val pump: Pump, val heater: Heater) // bootstrap from an injector // ---- // heater : Heater = ElectricHeater() // pump : Pump = Thermosiphon(heater) // coffeeMaker = CoffeeMaker(heater,pump) val coffeeMaker = Injector.get<CoffeeMaker>()

18. { Thermosiphon(get()) } { ElectricHeater() } Provide Provide

19. Koin

20. - Intuitive DSL to describe it - Lightweight container to

    run it - Simple API to use it - Pure Kotlin!

21. repositories { jcenter() } dependencies { // Koin for Kotlin

    implementation ‘org.koin:koin-core:$version’ } Gradle Setup

22. // declare definitions here module { }

23. module { // definition single | factory { instance creation

    expression } }

24. class ElectricHeater : Heater class Thermosiphon(val heater: Heater) : Pump

    class CoffeeMaker(val pump: Pump, val heater: Heater)

25. 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

26. 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 coffeeParts = module { single<Pump>{ Thermosiphon(get()) } single<Heater> { ElectricHeater() } } * also multi modules

27. Koin Component a class that can use the Koin container

28. ✅ 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…)

29. class CoffeeApp : KoinComponent { val coffeeMaker: CoffeeMaker by inject()

    fun run() { coffeeMaker.brew() } }

30. The CoffeeApp

31. startKoin to start the Koin container

32. class CoffeeApp : KoinComponent { val coffeeMaker: CoffeeMaker by inject()

    fun run() { coffeeMaker.brew() } } fun main(vararg args: String) { }

33. fun run() { coffeeMaker.brew() } } fun main(vararg args: String)

    { startKoin { } }

34. fun run() { coffeeMaker.brew() } } fun main(vararg args: String)

    { startKoin { modules(coffeeMakerModule) } }

35. fun run() { coffeeMaker.brew() } } fun main(vararg args: String)

    { startKoin { modules(coffeeMakerModule) } CoffeeApp().run() }

36. ~ ~ ~ heating ~ ~ ~ => => pumping

    => => [_]P coffee! [_]P
37. None

38. Can’t create Android components directly

39. Activity, Fragment, Service … are extended as KoinComponent! out of

    the box! ✅ Koin extensions for Android

40. repositories { jcenter() } dependencies { // Koin for Android

    implementation ‘org.koin:koin-android:$version’ } Gradle Setup

41. class MyApplication : Application() { override fun onCreate() { super.onCreate()

    // Add Android Koin Logger startKoin { androidLogger() modules(coffeeMakerModule) } } }

42. class MyApplication : Application() { override fun onCreate() { super.onCreate()

    // Reference Android context in Koin startKoin { androidLogger() androidContext(this@MyApplication) modules(coffeeMakerModule) } } }

43. class MyActivity : AppCompatActivity() { val coffeeMaker: CoffeeMaker by inject()

    }

44. Get the Android context?

45. class MyApplication : Application() { override fun onCreate() { super.onCreate()

    // Reference Android context in Koin startKoin { androidLogger() androidContext(this@MyApplication) modules(coffeeMakerModule) } } }

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 coffeeMaker : CoffeeMaker) val myModule = module {

    // will create MyPresenter on each call factory { MyPresenter(get()) } }

50. class MyPresenter(val coffeeMaker : CoffeeMaker) val myModule = module {

    // will create MyPresenter on each call factory { MyPresenter(get()) } } 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:$version’ implementation ‘org.koin:koin-androidx-viewmodel:$version’ } Gradle Setup

53. ✅ Koin extensions for Android ViewModel

54. class MyViewModel(val coffeeMaker : CoffeeMaker) : ViewModel() val coffeeMakerModule =

    module { viewModel { MyViewModel(get()) } }

55. //... viewModel { MyViewModel(get()) } } class MyActivity : AppCompatActivity()

    { // inject ViewModel val myViewModel: MyViewModel by viewModel()

56. //... viewModel { MyViewModel(get()) } } class MyFragment : Fragment()

    { // inject ViewModel val myViewModel: MyViewModel by viewModel()

57. //... viewModel { MyViewModel(get()) } } class MyFragment : Fragment()

    { // inject ViewModel from parent activity val myViewModel: MyViewModel by sharedViewModel()

58. Injecting Bundle State in ViewModel

59. repositories { jcenter() } dependencies { // Koin for Android

    Fragments feature implementation ‘org.koin:koin-androidx-viewmodel:$version’ } Gradle Setup 2.1.0-alpha-4

60. // Inject your state class StateViewModel(val state: SavedStateHandle) : ViewModel()

    // use injection parameter to get state viewModel { (handle: SavedStateHandle, id: String) -> StateViewModel(handle, id, get()) } // Provide initial state as parameter class MVVMActivity : AppCompatActivity() { val mySavedVM: StateViewModel by viewModel { parametersOf(Bundle(), "vm1") } }

61. // Inject your state class StateViewModel( val handle: SavedStateHandle, val

    id: String, val service: SimpleService) : ViewModel() // use injection parameter to get state viewModel { (handle: SavedStateHandle) -> StateViewModel(handle, id, get()) } // Provide initial state as parameter class MVVMActivity : AppCompatActivity() { val mySavedVM: StateViewModel by viewModel { parametersOf(Bundle(), "vm1") } }

62. // Inject your state class StateViewModel( val handle: SavedStateHandle, val

    id: String, val service: SimpleService) : ViewModel() // use injection parameter to get state viewModel { (handle: SavedStateHandle, id: String) -> StateViewModel(handle, id, get()) } // Provide initial state as parameter class MVVMActivity : AppCompatActivity() { val mySavedVM: StateViewModel by viewModel { parametersOf(Bundle()) } }

63. Inject your Fragments

64. repositories { jcenter() } dependencies { // Koin for Android

    Fragments feature implementation ‘org.koin:koin-androidx-fragment:$version’ } Gradle Setup 2.1.0-alpha-4

65. // Use constructor injection :) class MyFragment(val session: Session) :

    Fragment() // Declare your fragment val module = module { single { Session() } fragment { MyFragment(get()) } } // Setup in Activity class MyMActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { // setup factory setupKoinFragmentFactory() super.onCreate(savedInstanceState)

66. // Use constructor injection :) class MyFragment(val session: Session) :

    Fragment() // Declare your fragment val module = module { single { Session() } fragment { MyFragment(get()) } } // Setup in Activity class MyMActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { // setup factory setupKoinFragmentFactory() super.onCreate(savedInstanceState)

67. // Setup in Activity class MyMActivity : AppCompatActivity() { override

    fun onCreate(savedInstanceState: Bundle?) { // setup factory setupKoinFragmentFactory() super.onCreate(savedInstanceState) // Call your Fragment supportFragmentManager.beginTransaction() .replace(R.id.fragment, MyFragment::class.java, null, null) .commit() } }

68. // Setup in Activity class MyMActivity : AppCompatActivity() { override

    fun onCreate(savedInstanceState: Bundle?) { // setup factory setupKoinFragmentFactory() super.onCreate(savedInstanceState) // Call your Fragment supportFragmentManager.beginTransaction() .replace(R.id.fragment, MyFragment::class.java, null, null) .commit() } }

69. Ktor Web Applications

70. repositories { jcenter() } dependencies { // Koin for Ktor

    compile ‘org.koin:koin-ktor:$version’ // Koin SLF4J Logger compile ‘org.koin:koin-logger-slf4j:$version’ } Gradle Setup

71. fun main(args: Array<String>) { // Start Ktor embeddedServer(Netty, commandLineEnvironment(args)).start() }

    fun Application.main() { install(DefaultHeaders) install(CallLogging) // Routing section routing { get("/hello") { call.respondText(...) } } }

72. fun main(args: Array<String>) { // Start Ktor embeddedServer(Netty, commandLineEnvironment(args)).start() }

    fun Application.main() { install(DefaultHeaders) install(CallLogging) // Routing section routing { get("/coffee") { call.respondText(...) } } }

73. fun Application.main() { install(DefaultHeaders) install(CallLogging) install(Koin) { slf4jLogger() modules(coffeeMakerModule) }

    // Routing section routing { get(“/coffee") { call.respondText(...) } } }

74. fun Application.main() { install(DefaultHeaders) install(CallLogging) install(Koin) { slf4jLogger() modules(coffeeMakerModule) }

    val coffeeMaker by inject() // Routing section routing { get("/coffee") { call.respondText(...) } } }

75. fun Application.main() { install(DefaultHeaders) install(CallLogging) install(Koin) { slf4jLogger() modules(coffeeMakerModule) }

    val coffeeMaker by inject() // Routing section routing { get("/coffee") { call.respondText(coffeeMaker.printBrew()) } } }

76. Application, Route, Routing … are extended as KoinComponent! out of

    the box! ✅ Koin extensions for Ktor

77. class ElectricHeater : Heater class Thermosiphon(val heater: Heater) : Pump

    class CoffeeMaker(val pump: Pump, val heater: Heater) val coffeeMakerModule = module(createdAtStart = true) { single<CoffeeMaker>() singleBy<Pump,Thermosiphon>() singleBy<Heater,ElectricHeater>() }

78. Testing easily with Koin ✅

79. repositories { jcenter() } dependencies { // Koin for Tests

    testImplementation ‘org.koin:koin-test:$version’ } Gradle Setup In rewrite!

80. Checking your modules ✔

81. class ModuleTest { @Test fun `check all definitions from coffeeMakerModule`()

    { startKoin { modules(coffeeMakerModule) }.checkModules() } }

82. ✅ Koin extensions with JUnit & Mockito

83. class CoffeeMakerTest : KoinTest { val coffeeMaker: CoffeeMaker by inject()

    val heater: Heater by inject() @Test fun testHeaterIsTurnedOnAndThenOff() { startKoin { modules(coffeeMakerModule) } } }

84. class CoffeeMakerTest : KoinTest { val coffeeMaker: CoffeeMaker by inject()

    val heater: Heater by inject() @Test fun testHeaterIsTurnedOnAndThenOff() { startKoin { modules(coffeeMakerModule) } declareMock<Heater>() } }

85. 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() } }

86. More about Koin✨

87. - Container DSL - Qualifiers (string/type) - Global vs isolated

    context - Scope API - Android, Scopes & lifecycle - Injection Parameters - AndroidX - Koin for Java - Koin for Ktor

88. Koin 2.0

89. Since first 1.0 version…

90. Simple DSL module, single, factory, get

91. Pragmatic API ✌ KoinComponent, get, inject

92. None
93. None

94. * startup & Kotlin overhead ** split modules startup if

    needed

95. Benchmarks https://github.com/InsertKoinIO/thermosiphon_dagger2koin https://github.com/Sloy/android-dependency-injection-performance https://github.com/arnaudgiuliani/android-dependency-injection-performance

96. http://bit.ly/ready4koin

97. - Container DSL - Qualifiers (string/type) - Global vs isolated

    context - Scope API - Android, Scopes & lifecycle - Injection Parameters - AndroidX - Koin for Java - Koin for Ktor

98. - Container DSL - Qualifiers (string/type) - Global vs isolated

    context - Scope API - Android, Scopes & lifecycle - Injection Parameters - AndroidX - Koin for Java - Koin for Ktor

99. Dependency injection & Service Locator?

100. Dependency injection & Service Locator

101. class Thermosiphon(val heater : Heater) : Pump class ElectricHeater() :

     Heater module { single<Pump>{ Thermosiphon(get()) } single<Heater> { ElectricHeater() } } Dependency Injection - Constructor injection configured via Koin DSL - Your classes are not dependant to Koin API - Instances are called by Koin Container - Functional DSL Configuration: parameters, context, scopes…

102. class CoffeeApp : KoinComponent { val coffeeMaker by inject<CoffeeMaker>() }

     Service Locator - Use the Koin API to retrieve a dependency - “Host” class not created by Koin

103. Is service locator bad?

104. class CoffeeApp : KoinComponent { // Lazily ask for instance

     val coffeeMaker : CoffeeMaker by inject() } Service Locator class CoffeeApp { lateinit var coffeeMaker : CoffeeMaker init { // ask injection of setters DI.inject(this) } } Setter Injection

105. 0

106. 80% of your Koin usage will be configuration 20% will

     be platform extensions Limit your dependency to Koin as much as possible

107. The choice between Service Locator and Dependency Injection is less

     important than the principle of separating service configuration from the use of services within an application. Martin Fowler

108. Functional Dependency Injection

109. Function and Container Context

110. val coffeeMakerModule = module { single { CoffeeMaker(get(),get()) } single<Pump>{

     Thermosiphon(get()) } single<Heater> { ElectricHeater() } } typealias Definition<T> = Scope.(DefinitionParameters) -> T

111. Definition Parameters DSL Extension Scope

112. Function to inject parameters

113. class MyPresenter(val id : String) val myModule = module {

     factory { (id : String) -> MyPresenter(id)} }

114. val myModule = module { factory { (id : String)

     -> MyPresenter(id)} } class MyActivity : AppCompatActivity(){ val presenter : MyPresenter by inject { parametersOf("42")} }

115. class MyViewModel(val id : String) val myModule = module {

     viewModel { (id : String) -> MyViewModel(id)} }

116. val myModule = module { viewModel { (id : String)

     -> MyViewModel(id)} } class MyActivity : AppCompatActivity(){ val presenter : MyViewModel by viewModel { parametersOf("42")} }

117. ✨ Simpler declaration with Reflection ✨

118. A.k.a “Get rid of get() get() get() get() get()”

119. Functional Dependency Injection 0

120. repositories { jcenter() } dependencies { // Koin for Android

     implementation ‘org.koin:koin-core-ext:$version’ } Gradle Setup

121. 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() } }

122. class ElectricHeater : Heater class Thermosiphon(val heater: Heater) : Pump

     class CoffeeMaker(val pump: Pump, val heater: Heater) val coffeeMakerModule = module { single<CoffeeMaker>() singleBy<Pump,Thermosiphon>() singleBy<Heater,ElectricHeater>() }

123. Available out of the box for pure JVM platforms (Ktor,

     TornadoFx…)

124. repositories { jcenter() } dependencies { // Koin for Android

     implementation ‘org.koin:koin-android-ext:$version’ implementation ‘org.koin:koin-androidx-ext:$version’ } Gradle Setup

125. class MyViewModel(val coffeeMaker : CoffeeMaker) : ViewModel() val coffeeMakerModule =

     module { viewModel<MyViewModel>() }

126. Add following pro guard rules https://insert-koin.io/docs/2.0/quick-references/experimental-features/#proguard-rule

127. Check performances Pure functional DSL declaration is 4x - 10x

     faster * definition execution time ** depending on devices (< Android 6)

128. Let’s migrate to Koin, what else?

129. Refactoring is not always sustainable

130. « Hard to switch from our current DI » Top

     #1 issue
131. None

132. What if you could… run it easily in a module

     ✨

133. startKoin { modules(…) } loadKoinModules(…) Definition<Heater> Definition<Pump> Definition<CoffeeMaker> unloadKoinModules(…)

134. Making dynamic modules with Koin - Load dynamic modules/definitions -

     Change implementation on the fly - Easy to compose step by step

135. Onboarding Wallet Profile Transactions Profile v2 Payments Card Management Onboarding

     Onboarding v2

136. Dynamic Modules Architecture - Registry / Plugin architecture - Feature

     <> Libraries isolation (modules) - Navigation, Feature Flagging, A/B testing …

137. What’s next?

138. None

139. Tips & Best pratices

140. Try the getting started projects * look at code samples

141. start.insert-koin.io

142. doc.insert-koin.io

143. Add it step by step to your project * start

     with small components

144. Check your modules ✅

145. Keep it simple

146. and …

147. StackOverflow, Github & Slack for any question

148. None

149. @insertkoin_io koin-developers

150. Thank you! All the community…

151. stable_version = “2.0.1" unstable_version = “2.1.0-alpha-4” repositories { jcenter() }

     dependencies { // Core features compile "org.koin:koin-core:$version" // Ktor compile "org.koin:koin-ktor:$version" compile "org.koin:koin-logger-slf4j:$version" // Android implementation "org.koin:koin-android:$version"

152. dependencies { // Core features compile "org.koin:koin-core:$version" // Ktor compile

     "org.koin:koin-ktor:$version" compile "org.koin:koin-logger-slf4j:$version" // Android implementation "org.koin:koin-android:$version" // Android + ViewModel implementation "org.koin:koin-android-viewmodel:$version" // JUnit & Mockito testImplementation "org.koin:koin-test:$version" }

153. dependencies { // Core features compile "org.koin:koin-core:$version" // Ktor compile

     "org.koin:koin-ktor:$version" compile "org.koin:koin-logger-slf4j:$version" // Android implementation "org.koin:koin-android:$version" // Android + ViewModel implementation "org.koin:koin-android-viewmodel:$version" // JUnit & Mockito testImplementation "org.koin:koin-test:$version" }

154. dependencies { // Core features compile "org.koin:koin-core:$version" // Ktor compile

     "org.koin:koin-ktor:$version" compile "org.koin:koin-logger-slf4j:$version" // Android implementation “org.koin:koin-android:$version” // Android + ViewModel implementation "org.koin:koin-android-viewmodel:$version" // JUnit & Mockito testImplementation "org.koin:koin-test:$version" }

155. dependencies { // Core features compile "org.koin:koin-core:$version" // Ktor compile

     "org.koin:koin-ktor:$version" compile "org.koin:koin-logger-slf4j:$version" // Android implementation "org.koin:koin-android:$version" // Android + ViewModel implementation "org.koin:koin-android-viewmodel:$version" // JUnit & Mockito testImplementation "org.koin:koin-test:$version" }

156. insert-koin.io

157. Arnaud Giuliani - @arnogiu Thank you!