Koin DSL

Quick reference for Koin DSL. For detailed guides see Core - Definitions and Core - Modules.

DSL Approaches

:::tip The Compiler Plugin DSL provides auto-wiring and compile-time safety. See Compiler Plugin Setup. :::

Application DSL

A KoinApplication instance represents your configured Koin container. This lets you set up logging, load properties, and register modules.

Creating a KoinApplication

Choose between two approaches:

• koinApplication { } - Creates a standalone KoinApplication instance
• startKoin { } - Creates a KoinApplication and registers it in the GlobalContext

// Standalone instance (useful for testing or custom contexts)
val koinApp = koinApplication {
    modules(myModule)
}

// Global instance (standard approach for applications)
startKoin {
    logger()
    modules(myModule)
}

Configuration Functions

Within koinApplication or startKoin, you can use:

• logger() - Set the logging level and Logger implementation (default: EmptyLogger)
• modules() - Load modules into the container (accepts list or vararg)
• properties() - Load a HashMap of properties
• fileProperties() - Load properties from a file
• environmentProperties() - Load properties from OS environment variables
• createEagerInstances() - Instantiate all definitions marked with createdAtStart
• allowOverride(Boolean) - Enable/disable definition overriding (default: true since 3.1.0)

Global vs Local Context

The key difference between koinApplication and startKoin:

• startKoin - Registers the container in GlobalContext, making it accessible via KoinComponent, by inject(), and other global APIs
• koinApplication - Creates an isolated instance you control directly

// Global context - standard usage
startKoin {
    logger()
    modules(appModule)
}

// Later, anywhere in your app:
class MyClass : KoinComponent {
    val service: Service by inject() // Uses GlobalContext
}

// Local context - advanced usage (testing, multi-context apps)
val customKoin = koinApplication {
    modules(testModule)
}.koin

val service = customKoin.get<Service>() // Use specific instance

Starting Koin

A complete Koin setup example:

startKoin {
    // Configure logging
    logger(Level.INFO)

    // Load properties
    environmentProperties()

    // Declare modules
    modules(
        networkModule,
        databaseModule,
        repositoryModule,
        viewModelModule
    )

    // Create eager singletons
    createEagerInstances()
}

Module DSL

For comprehensive module and definition documentation, see:

• Definitions - All definition types with DSL and Annotations
• Modules - Module organization and composition
• Definitions Reference - Quick lookup table

Quick Reference

Basic Module

val myModule = module {
    single<Database>()
    single<UserRepository>()
    factory<UserPresenter>()
}

Module Composition

val appModule = module {
    includes(networkModule, databaseModule)
    single<AppConfig>()
}

startKoin {
    modules(appModule)
}

See Modules - includes() for details.