What is Koin?

A pragmatic lightweight dependency injection framework for Kotlin developers. Written in pure Kotlin using functional resolution only: no proxy, no code generation, no reflection!

Koin is a DSL, a lightweight container and a pragmatic API.

Get started Setup

// Stable Koin Version
koin_version = "2.1.6"
// Untable Koin Version
koin_version = "2.2.0-rc-3"

repositories {
  jcenter()    
}
dependencies {
    // Koin for Kotlin
    compile "org.koin:koin-core:$koin_version"
}

repositories {
  jcenter()    
}
dependencies {
    // Koin for Android
    compile "org.koin:koin-android:$koin_version"
    // or Koin for Lifecycle scoping
    compile "org.koin:koin-android-scope:$koin_version"
    // or Koin for Android Architecture ViewModel
    compile "org.koin:koin-android-viewmodel:$koin_version"
}

repositories {
  jcenter()    
}
dependencies {
    // Koin for Android
    compile "org.koin:koin-android:$koin_version"
    // or Koin for Lifecycle scoping
    compile "org.koin:koin-androidx-scope:$koin_version"
    // or Koin for Android Architecture ViewModel
    compile "org.koin:koin-androidx-viewmodel:$koin_version"
    // or Koin for Android Fragment Factory (unstable version)
    compile "org.koin:koin-androidx-fragment:$koin_version"
}

repositories {
  jcenter()    
}
dependencies {
    // Koin for Ktor
    compile "org.koin:koin-ktor:$koin_version"
}

// Given some classes class Controller(val service : BusinessService) class BusinessService() // just declare it val myModule = module { single { Controller(get()) } single { BusinessService() } }

class MyApplication : Application() { override fun onCreate(){ super.onCreate() // start Koin! startKoin { // declare used Android context androidContext(this@MyApplication) // declare modules modules(myModule) } } }

// Just inject in a simple Activity class MyActivity() : AppCompatActivity() { // lazy inject BusinessService into property val service : BusinessService by inject() override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // or directly get any instance val service : BusinessService = get() } }

// Injected by constructor class MyViewModel(val repo : MyRepository) : ViewModel() // declared ViewModel using the viewModel keyword val myModule : Module = module { viewModel { MyViewModel(get()) } single { MyRepository() } } // Just get it class MyActivity() : AppCompatActivity() { // lazy inject MyViewModel val myViewModel : MyViewModel by viewModel() }

// Just tag your class with KoinTest to unlick your testing power class SimpleTest : KoinTest { // lazy inject BusinessService into property val service : BusinessService by inject() @Test fun myTest() { // You can start your Koin configuration startKoin { modules(myModules) } // or directly get any instance val service : BusinessService = get() } }

What is Koin?

Declare a module

Start Koin

Inject in Android

Inject by Constructor

Ready for ViewModel

Easy testing