Android Architecture Design With Koin

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Android Architecture Design With Koin Arnaud Giuliani @arnogiu

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Koin Project Lead Google Dev Expert - Kotlin @arnogiu Arnaud GIULIANI

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Architecture Recipes With Koin

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Koin Core Concepts 🛠

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Just use Koin, what else?

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class ClassA() class ClassB(val a : ClassA)

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class ClassA() class ClassB(val a : ClassA) module { }

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class ClassA() class ClassB(val a : ClassA) module { single { ClassB() } }

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class ClassA() class ClassB(val a : ClassA) module { single { ClassA() } single { ClassB(???) } }

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class ClassA() class ClassB(val a : ClassA) module { single { ClassA() } single { ClassB(get()) } } - Constructor injection con fi gured via Koin DSL - Instances are called by Koin Container

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class MyApp { val classB : ClassB }

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class MyApp : KoinComponent { val classB : ClassB }

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class MyApp : KoinComponent { val classB by inject() } - Use the Koin API to retrieve a dependency - Host class is not created by Koin MyApp().classB

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Classical MVP-MVVM 🎯

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https:/ /github.com/InsertKoinIO/architecture-samples/tree/dev-koin https:/ /github.com/android/architecture-samples

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Tasks Repository Tasks DataSource Tasks Local DataSource TasksViewModel TasksActivity Tasks Database

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Since Koin 3.x! // Android implementation "io.insert-koin:koin-android:$koin_version" implementation "io.insert-koin:koin-androidx-viewmodel:$koin_version" implementation "io.insert-koin:koin-androidx-scope:$koin_version" implementation "io.insert-koin:koin-androidx-fragment:$koin_version"

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Tasks DataSource class TasksRemoteDataSource : TasksDataSource // Koin DSL single { TasksRemoteDataSource() }

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Tasks DataSource Tasks Local DataSource class TasksRemoteDataSource : TasksDataSource class TasksLocalDataSource( private val tasksDao: TasksDao, private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO ) : TasksDataSource // Koin DSL single { TasksRemoteDataSource() } single { TasksLocalDataSource(get(),get()) }

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Tasks DataSource Tasks Local DataSource class TasksRemoteDataSource : TasksDataSource class TasksLocalDataSource( private val tasksDao: TasksDao, private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO ) : TasksDataSource // Koin DSL single(named("RemoteDS")) { TasksRemoteDataSource() } single(named("LocalDS")) { TasksLocalDataSource(get(),get()) }

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class DefaultTasksRepository( private val tasksRemoteDataSource: TasksDataSource, private val tasksLocalDataSource: TasksDataSource, private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO ) : TasksRepository // Koin DSL single { DefaultTasksRepository( get(), get(), get() ) } Tasks Repository

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// Koin DSL single { Room.databaseBuilder( androidContext().applicationContext, ToDoDatabase::class.java, "Tasks.db" ).build() } single { get().taskDao() } Tasks Database

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// Koin DSL single { Room.databaseBuilder( androidContext().applicationContext, ToDoDatabase::class.java, "Tasks.db" ).build() } single { get().taskDao() } Tasks Database

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class TasksViewModel( private val tasksRepository: TasksRepository, private val savedStateHandle: SavedStateHandle ) : ViewModel() // Koin DSL viewModel { TasksViewModel(get(),get()) } TasksViewModel

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// by ViewModel() in Activity & Fragment class TasksActivity : AppCompatActivity() { // also inject SavedStateHandle val viewModel : TasksViewModel by viewModel() } TasksActivity

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Tasks Repository Tasks DataSource Tasks Local DataSource TasksActivity Tasks Database

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Tasks Repository Tasks DataSource Tasks Local DataSource TasksPresenter TasksActivity Tasks Database

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class TasksPresenter( private val tasksRepository: TasksRepository, private val view: TasksView ) // Koin DSL - Parameter injection for Presenter factory { TasksPresenter(get(), ??? ) } TasksViewPresenter

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class TasksPresenter( private val tasksRepository: TasksRepository, private val view: TasksView ) // Koin DSL - Parameter injection for Presenter factory { (view: TasksView) -> TasksPresenter(get(),view) } TasksViewPresenter

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class TasksActivity : TasksView, AppCompatActivity() { // inject itself as a view val presenter : TasksPresenter by inject { parametersOf(this) } } TasksView

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val appModule = module { // Presentation Layers viewModel { TasksViewModel(get(),get()) } factory { (view: TasksView) -> TasksPresenter(get(),view) } // Repository single { DefaultTasksRepository(get(named("RemoteDS")),get(named("LocalDS")),get()) } // Data Sources single(named("RemoteDS")) { TasksRemoteDataSource() } single(named("LocalDS")) { TasksLocalDataSource(get(),get()) } // Room single { Room.databaseBuilder(...).build() } single { get().taskDao() } }

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- Layers, features … - Granularity & Testability Organising Modules? 🤔

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val dataModule = module { } val uiModule = module { } val appModule = dataModule + uiModule startKoin { modules(appModule) }

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Clean Architecture 🏗

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Tasks Repository Tasks DataSource Tasks Local DataSource TasksViewModel TasksActivity Tasks Database

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Tasks Repository Tasks DataSource Tasks Local DataSource TasksViewModel TasksActivity Tasks Database GetTaskUseCase

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class TasksViewModel( private val getTaskUseCase: GetTaskUseCase, private val savedStateHandle: SavedStateHandle ) : ViewModel() // Koin DSL viewModel { TasksViewModel(get(),get()) } TasksViewModel

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class GetTaskUseCase( private val tasksRepository: TasksRepository ) // Koin DSL // Don’t hold instance - ensure it’s stateless factory { GetTaskUseCase(get()) } GetTaskUseCase

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val appModule = module { // Presentation Layers viewModel { TasksViewModel(get(),get()) } factory { (view: TasksView) -> TasksPresenter(get(),view) } // Usecase factory { GetTaskUseCase(get()) } // Repository single { DefaultTasksRepository(get(named("RemoteDS")),get(named("LocalDS")),get()) } // Data Sources single(named("RemoteDS")) { TasksRemoteDataSource() } single(named("LocalDS")) { TasksLocalDataSource(get(),get()) } // Room single { Room.databaseBuilder(...).build() } single { get().taskDao() } }

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Let’s wrap up 👍

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Tasks Repository Tasks DataSource Tasks Local DataSource TasksPresenter TasksActivity Tasks Database TasksViewModel Koin API factory or viewModel single single single

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Koin API factory or viewModel single single single Tasks Repository Tasks DataSource Tasks Local DataSource TasksViewModel TasksActivity Tasks Database GetTaskUseCase TasksPresenter factory

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Koin API factory or viewModel single single single Repository DataSource Local DataSource ViewModel Android UI Database UseCase / Interactor Presenter factory

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Working with Scopes 🚑

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Why do we need a scope? 📦 keep instances ⏱ specific time

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What about Android scope? We maintain instances for the duration of an Android component lifecycle.

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Follow the Android Components

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class MyActivity : AppCompatActivity() { val myPresenter : MyPresenter by inject() } // Koin DSL factory { MyPresenter(...) } 💥

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Android Scope

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class MyActivity : ScopeActivity() { // Resolved in MyActivity's scope val myPresenter : MyPresenter by inject() val myAdapter : MyAdapter by inject() } // Koin DSL scope { scoped { MyPresenter() } scoped { MyAdapter(get()) } } class MyAdapter(val presenter : Mypresenter) 💥 ScopeActivity use Activity’s scope by default

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ViewModel

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class MyActivity : Activity() { val myViewModel : MyViewModel by viewModel() } // Koin DSL viewModel { MyViewModel() } ♻ class MyViewModel() : ViewModel()

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class MyActivity : ScopeActivity() { // Override current scope to Activity's scope by default override val scope : Scope by activityRetainedScope() val myViewModel : MyViewModel by viewModel() val myAdapter : MyAdapter by inject() } All components are backed By ViewModel ✅

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Navigation Graph ViewModel

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// Android Nav implementation “io.insert-koin:koin-androidx-navigation:$koin_version"

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class NavViewModel() : ViewModel() // Koin DSL viewModel { NavViewModel() } NavViewModel

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class MyFragment : Fragment() { val navViewModel : NavViewModel by koinNavGraphViewModel(R.id.nav_graph) } MyFragment Nav Graph

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Scopes - Wrap up 👍

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// Koin DSL scope { scoped { MyPresenter() } scoped { MyAdapter(get()) } } Define a scope class MyActivity : ScopeActivity() { } interface AndroidScopeComponent { override val scope : Scope by activityScope() } Use a scope with Android API

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// create scope getKoin().createScope(...) // ... get it elsewhere val scope = getKoin().getScope(...) scope.get<>() Get the Scope API class MyFragment : Fragment() { val navViewModel : NavViewModel by koinNavGraphViewModel(R.id.nav_graph) } ViewModel scoped to Nav Graph

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Koin API factory or viewModel single single single Repository DataSource Local DataSource ViewModel Android UI Database Presenter

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Koin API factory, viewModel or Scope single single single Repository DataSource Local DataSource ViewModel Android UI Database Presenter

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Keep your Koin con fi g simple ✨

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Less Code = Less Bugs Chet Haase

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New Architectures! 🦄

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Jetpack Compose 🦄

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Injecting in Compose

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// Android Nav implementation “io.insert-koin:koin-androidx-compose:$koin_version”

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// Retrieving instance in a composable @Composable fun App() { val myService = get() // or by inject() } Getting instances in a Composable // Default parameter value @Composable fun App(myService: MyService = get()) { }

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// Retrieving ViewModel in a composable @Composable fun App() { val myViewModel = getViewModel() // or by viewModel() } Getting ViewModel in a Composable // Default parameter value @Composable fun App(myViewModel: MyViewModel = getViewModel()) { }

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https:/ /github.com/InsertKoinIO/compose-samples Jetpack Compose Samples

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Koin API factory or viewModel single single single Repository DataSource Local DataSource ViewModel Android UI Database Presenter

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Koin API factory or viewModel single single single Repository DataSource Local DataSource ViewModel Composable Database Presenter

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Dependency Injection For Kotlin Multiplatform ⭐

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Repository DataSource Local DataSource Presentation Android UI Database

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Repository DataSource Local DataSource Native UI (Android, iOS) Database Presentation

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Shared Kotlin Common Repository DataSource Local DataSource Native UI (Android, iOS) Database Presentation

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People In Space https:/ /github.com/joreilly/PeopleInSpace

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Android App Common Code iOS App Backend & web app

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Common Code

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Common DI Modules

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Kermit Logging Json Serialization Ktor Http Client + API Component Data Repository

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Json Serialization Ktor Http Client + API Component Data Repository Kermit Logging => Data Storage with SQLDelight

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JVM Impl iOS Impl

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val appModule = module { viewModel { PeopleInSpaceViewModel(get()) } } ViewModel -> Repository

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Koin API factory or viewModel single single single Kotlin Multiplatform API 🚀 Repository DataSource Local DataSource Native UI (Android, iOS) Database Presentation

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New features! 🌈

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New Feature Proposal ✨

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Limits of Koin DSL 🤨

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Kotlin Compiler Plugin! 🛠

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KSP Powered 🔥 👉 Generate Koin stu ff DSL for you https:/ /github.com/google/ksp

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Koin Semantic 🤔

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koin_annotations_version = “1.0.0-beta-2” implementation "io.insert-koin:koin-annotations:$koin_ksp_version" ksp "io.insert-koin:koin-ksp-compiler:$koin_ksp_version"

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Tasks Repository Tasks DataSource Tasks Local DataSource TasksViewModel TasksActivity Tasks Database

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De fi nitions

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Tasks DataSource class TasksRemoteDataSource : TasksDatasource

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Tasks DataSource @Single class TasksRemoteDataSource : TasksDatasource

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Tasks DataSource Tasks Local DataSource class TasksRemoteDataSource : TasksDatasource class TasksLocalDataSource( private val tasksDao: TasksDao, private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO ) : TasksDatasource

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Tasks DataSource Tasks Local DataSource @Single class TasksRemoteDataSource : TasksDatasource @Single class TasksLocalDataSource( private val tasksDao: TasksDao, private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO ) : TasksDatasource

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Tasks DataSource Tasks Local DataSource @Single @Named("RemoteDS") class TasksRemoteDataSource : TasksDatasource @Single @Named("LocalDS") class TasksLocalDataSource( private val tasksDao: TasksDao, private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO ) : TasksDatasource

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@Single class DefaultTasksRepository( private val tasksRemoteDataSource: TasksDataSource, private val tasksLocalDataSource: TasksDataSource, private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO ) : TasksRepository Tasks Repository

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@Single class DefaultTasksRepository( @Named("RemoteDS") private val tasksRemoteDataSource: TasksDataSource, @Named("LocalDS") private val tasksLocalDataSource: TasksDataSource, private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO ) : TasksRepository Tasks Repository

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class TasksViewModel( private val tasksRepository: TasksRepository, private val savedStateHandle: SavedStateHandle ) : ViewModel() TasksViewModel

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@KoinViewModel class TasksViewModel( private val tasksRepository: TasksRepository, private val savedStateHandle: SavedStateHandle ) : ViewModel() TasksViewModel

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// by ViewModel() in Activity & Fragment class TasksActivity : AppCompatActivity() { // also inject SavedStateHandle val viewModel : TasksViewModel by viewModel() } TasksActivity

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class TasksPresenter( private val tasksRepository: TasksRepository, private val view: TasksView ) TasksViewPresenter

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@Factory class TasksPresenter( private val tasksRepository: TasksRepository, private val view: TasksView ) TasksViewPresenter

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@Factory class TasksPresenter( private val tasksRepository: TasksRepository, @InjectedParam private val view: TasksView ) TasksViewPresenter

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class TasksActivity : TasksView, AppCompatActivity() { // inject itself as a view val presenter : TasksPresenter by inject { parametersOf(this) } } TasksView

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Tasks Repository Tasks DataSource Tasks Local DataSource TasksPresenter TasksActivity Tasks Database TasksViewModel Koin API @Factory or @koinViewModel @Single @Single @Single

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Modules

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Gathering definitions into Modules @Module class AppModule

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Gathering definitions into Modules @Module @ComponentScan("com.my.app") class AppModule

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import org.koin.ksp.generated.* startKoin { modules( // Class Module AppModule().module ) } Starting with Modules

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import org.koin.ksp.generated.* startKoin { modules( // DSL Module otherDSLModule, // Class Module AppModule().module ) } Mix Classes & DSL Modules

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@Module class DatabaseModule { @Single fun taskDao(db : ToDoDatabase) : TaskDao = db.taskDao() } Tasks Database

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@Module class DatabaseModule { @Single fun taskDao(db : ToDoDatabase) : TaskDao = db.taskDao() } Tasks Database

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Kotlin Compiler Plugin ☢ Code Generation

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Fast Compilation Time 🏎 ~2 sec - 1000 components

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Easy to Debug 🚒 Generated Koin DSL modules

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DSL and Annotations Choose what is best for you 👍

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👉 https:/ /github.com/InsertKoinIO/ koin-annotations

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What’s Next? 🚀

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Koin Downloads Volume 📦 📦 5M Downloads in 2020 9M Downloads in 2021 🚀✨🌈 2022: Trends of 5M / Month

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🗓 Roadmap 2022 Structured Release Cycle (~6months) - Fix Version (bug fi xes, fi x updates) - Minor Version (deprecations, minor features…) - Major Version (hard breaking …)

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🗓 Roadmap 2022 Q4 Releases: Koin 3.3, Koin for Compose End of Track: Koin 3.1 Q2 Releases: Koin 3.2, Koin Annotations 1.0 👉 New DSL, Module includes …

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⚠ End of support for Koin 2.X insert-koin.io/docs/migration/migrate

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// Latest version! koin_version = "3.1.6" // Current beta koin_version = "3.2.0-beta-1"