Sharing Patterns

This guide covers patterns for organizing Koin modules in Kotlin Multiplatform projects.

info

For basic KMP setup, see KMP Setup. For definition types, see Definitions.

The Shared Module Pattern

Create a common initialization function that can be extended by each platform:

// commonMain/kotlin/di/KoinHelper.kt
fun initKoin(config: KoinAppDeclaration? = null): KoinApplication {
    return startKoin {
        includes(config)  // Platform-specific extensions
        modules(
            sharedModule,
            dataModule,
            domainModule,
            platformModule
        )
    }
}

Module Organization

Examples use Compiler Plugin DSL. You can also use Annotations or Classic DSL.

By Layer

// commonMain/kotlin/di/modules/

// Data layer
val dataModule = module {
    single<ApiClient>()
    single<UserRepository>()
    single<ProductRepository>()
}

// Domain layer
val domainModule = module {
    factory<GetUserUseCase>()
    factory<GetProductsUseCase>()
    factory<CreateOrderUseCase>()
}

// Shared module aggregates all
val sharedModule = module {
    includes(dataModule, domainModule)
}

By Feature

// User feature
val userModule = module {
    single<UserRepository>()
    factory<GetUserUseCase>()
    factory<UpdateUserUseCase>()
}

// Product feature
val productModule = module {
    single<ProductRepository>()
    factory<GetProductsUseCase>()
    factory<SearchProductsUseCase>()
}

// Order feature
val orderModule = module {
    single<OrderRepository>()
    factory<CreateOrderUseCase>()
    factory<GetOrderHistoryUseCase>()
}

Platform Extensions

Platform modules use Classic DSL with lambdas when custom construction logic is needed.

Android Extension

// androidMain/kotlin/di/KoinAndroid.kt
fun initKoinAndroid(context: Context) {
    initKoin {
        androidContext(context)
        androidLogger()
        modules(androidModule)
    }
}

val androidModule = module {
    single<PlatformContext> { AndroidContext(get()) }
    single<FileStorage> { AndroidFileStorage(get()) }
    single<NetworkMonitor> { AndroidNetworkMonitor(get()) }
}

iOS Extension

// iosMain/kotlin/di/KoinIos.kt
fun initKoinIos() {
    initKoin {
        modules(iosModule)
    }
}

val iosModule = module {
    single<PlatformContext> { IosContext() }
    single<FileStorage> { IosFileStorage() }
    single<NetworkMonitor> { IosNetworkMonitor() }
}

Desktop Extension

// desktopMain/kotlin/di/KoinDesktop.kt
fun initKoinDesktop() {
    initKoin {
        printLogger()
        modules(desktopModule)
    }
}

val desktopModule = module {
    single<PlatformContext> { DesktopContext() }
    single<FileStorage> { DesktopFileStorage() }
}

Expect/Actual Module Pattern

Common Definition

// commonMain/kotlin/di/PlatformModule.kt
expect val platformModule: Module

Platform Implementations

// androidMain
actual val platformModule = module {
    single<DatabaseDriver> { AndroidSqliteDriver(AppDatabase.Schema, get(), "app.db") }
    single<HttpEngine> { Android.create() }
    single<Settings> { AndroidSettings(get()) }
}

// iosMain
actual val platformModule = module {
    single<DatabaseDriver> { NativeSqliteDriver(AppDatabase.Schema, "app.db") }
    single<HttpEngine> { Darwin.create() }
    single<Settings> { NSUserDefaultsSettings(NSUserDefaults.standardUserDefaults) }
}

// jsMain
actual val platformModule = module {
    single<DatabaseDriver> { JsSqliteDriver() }
    single<HttpEngine> { Js.create() }
    single<Settings> { LocalStorageSettings() }
}

Compose Multiplatform

For multiplatform ViewModel, see ViewModel.

Shared ViewModel

// commonMain
@KoinViewModel
class UserViewModel(
    private val getUserUseCase: GetUserUseCase
) : ViewModel() {
    private val _state = MutableStateFlow<UserState>(UserState.Loading)
    val state = _state.asStateFlow()

    fun loadUser(id: String) {
        viewModelScope.launch {
            _state.value = UserState.Success(getUserUseCase(id))
        }
    }
}

Shared UI

// commonMain
@Composable
fun UserScreen(
    viewModel: UserViewModel = koinViewModel()
) {
    val state by viewModel.state.collectAsState()

    when (val s = state) {
        is UserState.Loading -> LoadingIndicator()
        is UserState.Success -> UserContent(s.user)
        is UserState.Error -> ErrorMessage(s.message)
    }
}

Testing

For KMP testing patterns, see Testing.

Best Practices

1. Single init function - One initKoin() in commonMain
2. Platform extensions via config - Use includes(config) pattern
3. Minimize platform modules - Only truly platform-specific code
4. Share ViewModel logic - Business logic in commonMain
5. Use expect/actual for factories - Platform-specific instance creation
6. Test in commonTest - Most tests can be shared

Next Steps

• KMP Setup - Basic KMP configuration
• ViewModel - Multiplatform ViewModel
• Advanced Patterns - Architecture patterns, testing, platform integration
• Koin for Compose - Compose Multiplatform