Getting Big Payouts with Koin -- Droidcon NYC

Thanks to its clean design, Koin is quickly gaining popularity as a service locator framework. Highlights include its excellent documentation, accessible api, and the pure Kotlin source code.

In this talk, we’ll go over basic usage like factories, singles, and modules. We’ll talk about scoping and lazy-loading modules, and we’ll look at its integration with Android screens and ViewModels. Then, and most importantly, we’ll see how we can use Koin to quickly and easily generate mocked dependencies for clean and hermetic tests.

Transcript

1. @rbusarow GETTING BIG PAYOUTS WITH KOIN Rick Busarow rickbusarow@gmail.com
2. @rbusarow What’s Koin?
3. What’s Koin? @rbusarow
4. What’s Koin? @rbusarow
5. What’s Koin? @rbusarow
6. @rbusarow Screen ViewModel UserId Repository Dao Room Database App Context Service Retrofit OkHttpClient Base Url
7. @rbusarow Normal Control Flow
8. @rbusarow class UserRepository { internal val service: UserService = retrofit.create<UserService>() internal val dao: UserDao = database.userDao } Normal Control Flow
9. @rbusarow class UserRepository { internal val okHttpClient: OkHttpClient = OkHttpClient() internal val retrofit: Retrofit = Retrofit.Builder() .baseUrl("https://example.dev") .client(okHttpClient) .build() internal val database: Database = Database.init(APP_CONTEXT) internal val service: UserService = retrofit.create<UserService>() internal val dao: UserDao = database.userDao } Normal Control Flow
10. @rbusarow class UserRepository { internal val okHttpClient: OkHttpClient = OkHttpClient() internal val retrofit: Retrofit = Retrofit.Builder() .baseUrl("https://example.dev") .client(okHttpClient) .build() internal val database: Database = Database.init(APP_CONTEXT) internal val service: UserService = retrofit.create<UserService>() internal val dao: UserDao = database.userDao } Normal Control Flow
11. @rbusarow Inversion of Control
12. @rbusarow Service Location Dependency Injection Inversion of Control
13. @rbusarow Service Location Dependency Injection class UserViewModel { private val repository = Locator.createRepository() } Inversion of Control
14. @rbusarow Service Location Dependency Injection class UserViewModel { private val repository = Locator.createRepository() } class UserViewModel(val repository: UserRepository) { lateinit var otherDependency : OtherDependency } Inversion of Control
15. @rbusarow Field Injection
16. @rbusarow class UserScreen : Fragment() { lateinit var viewModel: UserViewModel } Field Injection
17. class UserScreen : Fragment() { lateinit var viewModel: UserViewModel override fun onAttach(context: Context) { Injector.inject(this) super.onAttach(context) } } object Injector { fun inject(screen: UserScreen) { screen.viewModel = TODO() } } @rbusarow Field Injection
18. class UserScreen : Fragment() { lateinit var viewModel: UserViewModel override fun onAttach(context: Context) { Injector.inject(this) super.onAttach(context) } } object Injector { fun inject(screen: UserScreen) { screen.viewModel = TODO() } } @rbusarow Field Injection
19. @rbusarow class UserScreen : Fragment() { lateinit var viewModel: UserViewModel override fun onAttach(context: Context) { Injector.inject(this) super.onAttach(context) } } object Injector { fun inject(screen: UserScreen) { screen.viewModel = TODO() } } Field Injection public mutable late init
20. @rbusarow Constructor Injection
21. @rbusarow class UserRepository( private val service: UserService, private val dao: UserDao ) { … } Constructor Injection
22. @rbusarow class UserViewModel { val repository = UserRepository(service = TODO(), dao = TODO()) } Constructor Injection
23. @rbusarow class UserViewModel { val client = OkHttpClient() val retrofit = Retrofit.Builder() .baseUrl("https://example.dev") .client(client) .build() val service = retrofit.create<UserService>() val database = Database.init(APP_CONTEXT) val dao = database.userDao val repository = UserRepository(service = service, dao = dao) } Constructor Injection
24. @rbusarow class UserViewModel { val client = OkHttpClient() val retrofit = Retrofit.Builder() .baseUrl("https://example.dev") .client(client) .build() val service = retrofit.create<UserService>() val database = Database.init(APP_CONTEXT) val dao = database.userDao val repository = UserRepository(service = service, dao = dao) } Constructor Injection
25. @rbusarow class UserViewModel(service: UserService, dao: UserDao) { val repository = UserRepository(service = service, dao = dao) } Constructor Injection
26. @rbusarow class UserViewModel( private val repository: UserRepository ) : ViewModel() Constructor Injection
27. @rbusarow class UserScreen : Fragment() { val viewModel = UserViewModel(repository = TODO()) } Constructor Injection
28. @rbusarow class UserScreen : Fragment() { lateinit var viewModel : UserViewModel override fun onAttach(context: Context) { Injector.inject(this) super.onAttach(context) } } Field Injection…
29. @rbusarow class UserScreen : Fragment() { lateinit var viewModel : UserViewModel override fun onAttach(context: Context) { Injector.inject(this) super.onAttach(context) } } Field Injection…
30. @rbusarow Service Location
31. @rbusarow class UserScreen : Fragment() { private val viewModel by lazy { ViewModelProviders .of(this) .get(UserViewModel::class.java) } override fun onAttach(context: Context) { Injector.inject(this) super.onAttach(context) } } Service Location
32. @rbusarow class UserScreen : Fragment() { private val viewModel by lazy { Locator.get<UserViewModel>() } override fun onAttach(context: Context) { Injector.inject(this) super.onAttach(context) } } Service Location
33. @rbusarow class UserScreen : Fragment() { private val viewModel by lazy { Locator.get<UserViewModel>() } override fun onAttach(context: Context) { Injector.inject(this) super.onAttach(context) } } Service Location object Locator { inline fun <reified T : ViewModel> get(): T = … }
34. @rbusarow class UserScreen : Fragment() { private val presenter by lazy { Locator.get<UserPresenter>() } private val viewModel by lazy { Locator.get<UserViewModel>() } override fun onAttach(context: Context) { Injector.inject(this) super.onAttach(context) } } Service Location object Locator { inline fun <reified T : ViewModel> get(): T = … }
35. @rbusarow class UserScreen : Fragment() { private val presenter by lazy { Locator.instance.get<UserPresenter>() } private val viewModel by lazy { Locator.instance.get<UserViewModel>() } override fun onAttach(context: Context) { Injector.inject(this) super.onAttach(context) } } interface Locator { fun <T : ViewModel> get(): T = … companion object { lateinit var instance: Locator } } Service Location
36. @rbusarow Koin KoinApplication
37. class Koin { val graph: Graph fun <T> inject(): Lazy<T> fun <T> get(): T fun <S, P> bind(s: S): S fun createScope(scopeId: ScopeID, qualifier: Qualifier): Scope } class KoinApplication { val koin = Koin() fun modules(modules: List<Module>): KoinApplication fun logger(logger: Logger): KoinApplication fun unloadModules(modules: List<Module>) fun close() } @rbusarow Koin & KoinApplication
38. class Koin { val graph: Graph fun <T> inject(): Lazy<T> fun <T> get(): T fun <S, P> bind(s: S): S fun createScope(scopeId: ScopeID, qualifier: Qualifier): Scope } class KoinApplication { val koin = Koin() fun modules(modules: List<Module>): KoinApplication fun logger(logger: Logger): KoinApplication fun unloadModules(modules: List<Module>) fun close() } @rbusarow Koin & KoinApplication
39. class Koin { val graph: Graph fun <T> inject(): Lazy<T> fun <T> get(): T fun <S, P> bind(s: S): S fun createScope(scopeId: ScopeID, qualifier: Qualifier): Scope } class KoinApplication { val koin = Koin() fun modules(modules: List<Module>): KoinApplication fun logger(logger: Logger): KoinApplication fun unloadModules(modules: List<Module>) fun close() } @rbusarow Koin & KoinApplication Not an Android Application
40. @rbusarow GlobalContext
41. @rbusarow object GlobalContext { internal var app: KoinApplication? = null fun get(): KoinApplication fun getOrNull(): KoinApplication? fun start(koinApplication: KoinApplication) fun stop() = synchronized(this) { app?.close() app = null } } GlobalContext
42. @rbusarow startKoin( ) koinApplication( )
43. @rbusarow fun startKoin(appDeclaration: KoinAppDeclaration): KoinApplication { val koinApplication = KoinApplication.create() GlobalContext.start(koinApplication) appDeclaration(koinApplication) koinApplication.createEagerInstances() return koinApplication } fun koinApplication(appDeclaration: KoinAppDeclaration): KoinApplication { val koinApplication = KoinApplication.create() appDeclaration(koinApplication) return koinApplication } startKoin & koinApplication
44. @rbusarow fun startKoin(appDeclaration: KoinAppDeclaration): KoinApplication { val koinApplication = KoinApplication.create() GlobalContext.start(koinApplication) appDeclaration(koinApplication) koinApplication.createEagerInstances() return koinApplication } fun koinApplication(appDeclaration: KoinAppDeclaration): KoinApplication { val koinApplication = KoinApplication.create() appDeclaration(koinApplication) return koinApplication } startKoin & koinApplication
45. @rbusarow fun startKoin(appDeclaration: KoinAppDeclaration): KoinApplication { val koinApplication = KoinApplication.create() GlobalContext.start(koinApplication) appDeclaration(koinApplication) koinApplication.createEagerInstances() return koinApplication } fun koinApplication(appDeclaration: KoinAppDeclaration): KoinApplication { val koinApplication = KoinApplication.create() appDeclaration(koinApplication) return koinApplication } startKoin & koinApplication
46. @rbusarow class MyApplication : Application() { override fun onCreate() { super.onCreate() } } MyApplication.kt
47. @rbusarow class MyApplication : Application() { override fun onCreate() { super.onCreate() startKoin { // route all Koin logs through android.util.Log androidLogger() } } } MyApplication.kt
48. @rbusarow private class TimberLogger(level: Level = Level.INFO) : Logger(level) { override fun log(level: Level, msg: MESSAGE) { if (this.level <= level) { when (this.level) { Level.DEBUG -> Timber.tag(KOIN_TAG).d(msg) Level.INFO -> Timber.tag(KOIN_TAG).i(msg) Level.ERROR -> Timber.tag(KOIN_TAG).e(msg) } } } } fun KoinApplication.timberLogger(level: Level = Level.INFO): KoinApplication { KoinApplication.logger = TimberLogger(level) return this } TimberLogger.kt
49. @rbusarow class MyApplication : Application() { override fun onCreate() { super.onCreate() Timber.plant(DebugTree()) startKoin { // route all Koin logs through Timber timberLogger() } } } MyApplication.kt
50. @rbusarow class MyApplication : Application() { override fun onCreate() { super.onCreate() Timber.plant(DebugTree()) startKoin { // route all Koin logs through Timber timberLogger() // provide Application context to the graph androidContext(this@MyApplication) } } } MyApplication.kt
51. @rbusarow class MyApplication : Application() { override fun onCreate() { super.onCreate() Timber.plant(DebugTree()) startKoin { // route all Koin logs through Timber timberLogger() // provide Application context to the graph androidContext(this@MyApplication) modules(koinDemoModules) } } } MyApplication.kt
52. @rbusarow Modules
53. @rbusarow val dataModule = module { } Modules
54. @rbusarow val dataModule = module { factory { } } Modules
55. @rbusarow val dataModule = module { factory { UserRepository() } } Modules
56. @rbusarow val dataModule = module { factory { Timber.v("Hello everyone!") UserRepository().also { Timber.v("Goodbye!") } } } Modules
57. @rbusarow val dataModule = module { factory { UserRepository() } } Modules
58. @rbusarow val dataModule = module { factory { UserRepository() } } Modules BeanDefinition Component
59. @rbusarow Connecting the Graph
60. class MyApplication : Application() { override fun onCreate() { super.onCreate() Timber.plant(DebugTree()) startKoin { // route all Koin logs through Timber timberLogger() // provide Application context to the graph androidContext(this@MyApplication) modules(koinDemoModules) } } } @rbusarow Connecting the Graph
61. class MyApplication : Application() { override fun onCreate() { super.onCreate() Timber.plant(DebugTree()) startKoin { // route all Koin logs through Timber timberLogger() // provide Application context to the graph androidContext(this@MyApplication) modules(koinDemoModules) } } } @rbusarow Connecting the Graph
62. @rbusarow val koinDemoModules: List<Module> get() = emptyListOf() val dataModule = module { factory { UserRepository() } } Connecting the Graph
63. @rbusarow val koinDemoModules: List<Module> get() = listOf(dataModule) val dataModule = module { factory { UserRepository() } } Connecting the Graph
64. @rbusarow class UserRepository { internal val database: Database = Database.init(APP_CONTEXT) internal val okHttpClient: OkHttpClient = OkHttpClient() internal val retrofit: Retrofit = Retrofit.Builder() .baseUrl("https://example.dev") .client(okHttpClient) .build() internal val service: UserService = retrofit.create<UserService>() internal val dao: UserDao = database.userDao } Connecting the Graph
65. @rbusarow class UserRepository( private val service: UserService, private val dao: UserDao ) { … } Modules
66. @rbusarow val dataModule = module { factory { UserRepository() } } Connecting the Graph
67. @rbusarow val dataModule = module { factory { Repository(service = get(), dao = get()) } } Modules
68. @rbusarow val dataModule = module { factory<UserService> { TODO() } factory<UserDao> { TODO() } factory { UserRepository(service = get(), dao = get()) } } Connecting the Graph
69. val dataModule = module { factory { OkHttpClient() } factory { Retrofit.Builder() .baseUrl("https://example.dev") .client(get<OkHttpClient>()) .build() } factory<UserService> { get<Retrofit>().create<UserService>() } factory<UserDao> { TODO() } factory { UserRepository(service = get(), dao = get()) } } @rbusarow Connecting the Graph
70. val dataModule = module { factory { OkHttpClient() } factory { Retrofit.Builder() .baseUrl("https://example.dev") .client(get<OkHttpClient>()) .build() } factory<UserService> { get<Retrofit>().create<UserService>() } factory<UserDao> { TODO() } factory { UserRepository(service = get(), dao = get()) } } @rbusarow Connecting the Graph
71. val dataModule = module { factory { OkHttpClient() } factory { Retrofit.Builder() .baseUrl("https://example.dev") .client(get<OkHttpClient>()) .build() } factory<UserService> { get<Retrofit>().create<UserService>() } factory { Database.init(androidContext()) } factory<UserDao> { get<Database>().userDao } factory { UserRepository(service = get(), dao = get()) } } @rbusarow Connecting the Graph
72. val dataModule = module { factory { OkHttpClient() } factory { Retrofit.Builder() .baseUrl("https://example.dev") .client(get<OkHttpClient>()) .build() } factory<UserService> { get<Retrofit>().create<UserService>() } factory { Database.init(androidContext()) } factory<UserDao> { get<Database>().userDao } factory { UserRepository(service = get(), dao = get()) } } @rbusarow Connecting the Graph
73. @rbusarow Connecting the Graph val dataModule = module { factory { OkHttpClient() } factory { Retrofit.Builder() .baseUrl("https://example.dev") .client(get<OkHttpClient>()) .build() } factory<UserService> { get<Retrofit>().create<UserService>() } factory { Database.init(androidContext()) } factory<UserDao> { get<Database>().userDao } factory { UserRepository(service = get(), dao = get()) } }
74. @rbusarow Modules val dataModule = module { factory<OkHttpClient> { OkHttpClient() } factory<Retrofit> { Retrofit.Builder() .baseUrl("https://example.dev") .client(get<OkHttpClient>()) .build() } factory<UserService> { get<Retrofit>().create<UserService>() } factory<UserDatabase> { Database.init(androidContext()) } factory<UserDao> { get<Database>().userDao } factory<UserRepository> { UserRepository(service = get(), dao = get()) } }
75. @rbusarow Modules val dataModule = module { factory<OkHttpClient> { OkHttpClient() } factory<Retrofit> { Retrofit.Builder() .baseUrl("https://example.dev") .client(get<OkHttpClient>()) .build() } factory<UserService> { get<Retrofit>().create<UserService>() } factory<UserDatabase> { Database.init(androidContext()) } factory<UserDao> { get<Database>().userDao } factory<UserRepository> { UserRepository(service = get(), dao = get()) } }
76. val dataModule = module { factory<OkHttpClient> { OkHttpClient() } factory<Retrofit> { Retrofit.Builder() .baseUrl("https://example.dev") .client(get<OkHttpClient>()) .build() } factory<UserService> { get<Retrofit>().create<UserService>() } factory<Database> { Database.init(androidContext()) } factory<UserDao> { get<Database>().userDao } factory<UserRepository> { UserRepository(service = get(), dao = get()) } } @rbusarow Connecting the Graph
77. val dataModule = module { single<OkHttpClient> { OkHttpClient() } single<Retrofit> { Retrofit.Builder() .baseUrl("https://example.dev") .client(get<OkHttpClient>()) .build() } single<UserService> { get<Retrofit>().create<UserService>() } single<Database> { Database.init(androidContext()) } factory<UserDao> { get<Database>().userDao } single<UserRepository> { UserRepository(service = get(), dao = get()) } } @rbusarow Modules
78. @rbusarow Accessing the Graph
79. @rbusarow class UserScreen { val repository: UserRepository = TODO() } Accessing the Graph
80. @rbusarow class UserScreen { val repository = GlobalContext.get().koin.get<UserRepository>() } Accessing the Graph
81. @rbusarow class UserScreen : KoinComponent { val repository = get<UserRepository>() } Accessing the Graph
82. @rbusarow class UserScreen : Fragment() { val repository = get<UserRepository>() } Accessing the Graph
83. @rbusarow class UserScreen : Fragment() { val repository = get<UserRepository>() } class UserViewModel(private val repository: UserRepository) : ViewModel() Accessing the Graph
84. @rbusarow val koinDemoModules: List<Module> get() = listOf(dataModule, viewModelModule) val viewModelModule = module { viewModel<UserViewModel> { UserViewModel(repository = get()) } } Accessing the Graph
85. @rbusarow val koinDemoModules: List<Module> get() = listOf(dataModule, viewModelModule) val viewModelModule = module { viewModel<ViewModel> { ViewModel(repository = get()) } } Accessing the Graph
86. @rbusarow class UserScreen : Fragment() { val viewModel = get<UserViewModel>() } class UserViewModel(private val repository: UserRepository) : ViewModel() Accessing the Graph
87. @rbusarow class UserScreen : Fragment() { val viewModel by viewModel<UserViewModel>() } class UserViewModel(private val repository: UserRepository) : ViewModel() Accessing the Graph
88. @rbusarow class UserScreen : Fragment() { val repository by inject<UserRepository>() val viewModel by viewModel<UserViewModel>() } class UserViewModel(private val repository: UserRepository) : ViewModel() Accessing the Graph
89. @rbusarow Parameters
90. @rbusarow class UserScreen : Fragment() { val repository by inject<UserViewModel>() val viewModel by viewModel<UserViewModel>() } class UserViewModel(private val repository: UserViewModel) : ViewModel() Parameters
91. @rbusarow class UserScreen : Fragment() { val repository by inject<UserRepository>() val viewModel by viewModel<UserViewModel>() } class UserViewModel( private val userId: String, private val repository: UserRepository ) : ViewModel() Parameters
92. @rbusarow class UserScreen : Fragment() { val repository by inject<UserRepository>() val viewModel by viewModel<UserViewModel>() } class UserViewModel( private val userId: String, private val repository: UserRepository ) : ViewModel() val viewModelModule = module { viewModel<UserViewModel> { (userId: String) -> ViewModel(userId = userId, repository = get()) } } Parameters
93. @rbusarow class UserScreen : Fragment() { val repository by inject<UserRepository>() val viewModel by viewModel<UserViewModel> { parametersOf(“50 Cent”) } } class UserViewModel( private val userId: String, private val repository: UserRepository ) : ViewModel() val viewModelModule = module { viewModel<UserViewModel> { (userId: String) -> UserViewModel(userId = userId, repository = get()) } } Parameters
94. @rbusarow Scope
95. @rbusarow val koinDemoModules: List<Module> get() = listOf(dataModule, scopedModule, viewModelModule) val scopedModule = module { scoped<Preferences> { Preferences() } } Scope
96. @rbusarow val koinDemoModules: List<Module> get() = listOf(dataModule, scopedModule, viewModelModule) val scopedModule = module { scoped<Preferences> { Preferences() } } object Scopes val Scopes.login: StringQualifier get() = named("login") Scope
97. @rbusarow val koinDemoModules: List<Module> get() = listOf(dataModule, scopedModule, viewModelModule) val scopedModule = module { scope(scopeName = Scopes.login) { scoped<Preferences> { Preferences() } } } object Scopes val Scopes.login: StringQualifier get() = named("login") Scope
98. @rbusarow val koinDemoModules: List<Module> get() = listOf(dataModule, scopedModule, viewModelModule) val scopedModule = module { scope(scopeName = Scopes.login) { scoped<Preferences> { Preferences() } } } class Anywhere : KoinComponent { val loginScope = getKoin().createScope(Scopes.login, named("login")) val preferences by loginScope.inject<Preferences>() } Scope
99. @rbusarow class Screen : Fragment() { val presenter by currentScope.inject<Presenter>() val viewModel by viewModel<ViewModel>() } val scopedModule = module { scope(named<Screen>()) { scoped<Presenter> { Presenter() } } scope(scopeName = Scopes.login) { scoped<Preferences> { Preferences() } } } Parameters
100. @rbusarow Testing
101. @rbusarow Overriding Modules
102. @rbusarow internal class UserRepositoryTest { val service = mockk<UserService>() val dao = mockk<UserDao>() lateinit var repo: UserRepository @BeforeEach fun beforeEach() { repo = UserRepository(service, dao) } } Testing
103. @rbusarow internal class UserRepositoryTest : KoinTest { val service = mockk<UserService>() val dao = mockk<UserDao>() lateinit var repo: UserRepository @BeforeEach fun beforeEach() { repo = UserRepository(service, dao) } } Testing
104. @rbusarow internal class UserRepositoryTest : KoinTest { … @BeforeEach fun beforeEach() { startKoin { modules(koinDemoModules) } repo = get<UserRepository>() } @AfterEach fun afterEach() { getKoin().close() } } Testing
105. @rbusarow internal class UserRepositoryTest : KoinTest { … val mocks = module(override = true) { single<UserService> { service } single<UserDao> { dao } } @BeforeEach fun beforeEach() { startKoin { modules(koinDemoModules) } repo = get<UserRepository>() } @AfterEach fun afterEach() { getKoin().close() } } Testing
106. @rbusarow internal class UserRepositoryTest : KoinTest { … val mocks = module(override = true) { single<UserService> { service } single<UserDao> { dao } } @BeforeEach fun beforeEach() { startKoin { modules(koinDemoModules) modules(mocks) } repo = get<UserRepository>() } … } Testing
107. @rbusarow Checking the Graph
108. @rbusarow internal class ModuleTest : KoinTest { @BeforeEach fun beforeEach() { startKoin { modules(koinDemoModules) } } @AfterEach fun afterEach() { getKoin().close() } @Test fun `check modules`() { getKoin().checkModules() } } Testing
109. @rbusarow Try it yourself!
110. @rbusarow Further Reading http://bit.ly/322XZr5 http://bit.ly/2L2IfO4 Koin Android documentation: Koin Core documentation: Koin Github: http://bit.ly/2ZkTk2d
111. rbusarow rbusarow rbusarow THANKS! Rick Busarow rickbusarow@gmail.com