Inyección de dependencias en KMP con Koin

¿Por qué DI en KMP?

// No annotation processing needed — Koin uses lambda DSL
// Add to build.gradle.kts:
// implementation("io.insert-koin:koin-core:3.5.0")
// androidMain: koin-android
// iosMain: no extra dep
fun main() { println("Koin works on all KMP targets") }

DSL de módulos de Koin

import org.koin.core.module.dsl.*
import org.koin.dsl.*
val appModule = module {
    single { HttpClient() }               // one instance
    single<UserRepository> { RemoteUserRepository(get()) }
    factory { GetUserUseCase(get()) }      // new instance each time
}

Módulo compartido en commonMain

// commonMain/di/SharedModule.kt
import org.koin.dsl.module
fun sharedModule() = module {
    single<UserRepository> { RemoteUserRepository(get()) }
    single { GetUserUseCase(get()) }
    single { UserViewModel(get()) }
}

Módulo de plataforma en androidMain

// androidMain/di/AndroidModule.kt
import io.ktor.client.engine.okhttp.*
import org.koin.dsl.module
fun androidModule() = module {
    single { OkHttp.create() }    // Ktor engine
    single { createHttpClient(get()) }
    includes(sharedModule())
}

startKoin en la aplicación de Android

// androidMain:
import org.koin.android.ext.koin.androidContext
import org.koin.core.context.startKoin
// In Application.onCreate():
startKoin {
    androidContext(this@MyApp)
    modules(androidModule())
}

Iniciar Koin en iOS

// iosMain/KoinInit.kt:
import org.koin.core.context.startKoin
fun initKoin() {
    startKoin {
        modules(iosModule())
    }
}
// Swift: KoinInitKt.doInitKoin() in AppDelegate

Resolver dependencias

import org.koin.core.component.KoinComponent
import org.koin.core.component.inject
class UserViewModel : KoinComponent {
    private val getUser: GetUserUseCase by inject()
    fun load(id: String) = runBlocking { getUser(id) }
}

Ámbitos de Koin para ViewModels

// androidMain (with koin-android):
import org.koin.androidx.viewmodel.dsl.viewModel
val androidVmModule = module {
    viewModel { UserViewModel(get()) }
}
// In Compose:
// val vm: UserViewModel = koinViewModel()

Pruebas con Koin

import org.koin.core.context.startKoin
import org.koin.core.context.stopKoin
import org.koin.dsl.module
class UserViewModelTest {
    @BeforeTest fun setup() {
        startKoin { modules(module {
            single<UserRepository> { FakeUserRepository() }
            single { GetUserUseCase(get()) }
        })}
    }
    @AfterTest fun teardown() = stopKoin()
}

Single frente a Factory y Scoped

import org.koin.dsl.module
val lifetimeModule = module {
    single { Database() }           // shared, one instance
    factory { Analytics() }         // new on each get()
    scope<ScreenScope> {
        scoped { ScreenViewModel() } // one per screen lifecycle
    }
}

Koin frente a DI manual y Hilt

fun main() {
    // Koin  : commonMain, runtime, lambda DSL
    // Hilt  : androidMain only, compile-time
    // Manual: no framework, explicit wiring in factory/module files
    println("Choose Koin for KMP; Hilt for Android-only projects")
}

Inyección diferida con by inject()

import org.koin.core.component.KoinComponent
import org.koin.core.component.inject
class AppService : KoinComponent {
    private val repo: UserRepository by inject()  // resolved on first use
    fun doWork() = println(repo.javaClass.simpleName)
}

Comprobación rápida

Repaso