A LightWeight DI framework

1. Koin
Koin - a lightweight DI framework

2. About me 1 year experience
Taiwan Android Developer Study Group(Android 讀
書會)
https://medium.com/@hung_yanbin
不上班狀態中

3. About me 1 year experience
Taiwan Android Developer Study Group(Android 讀
書會)
https://medium.com/@hung_yanbin
不上班狀態中

4. About me 1 year experience
Taiwan Android Developer Study Group(Android 讀
書會)
https://medium.com/@hung_yanbin
不上班狀態中
即將加入 Piccollage !!

5. Why Koin?
● No code generation
● No reflection
● Support Android Architecture Component
● Support Java
● Easy to use

6. Why Koin?
● No code generation
● No reflection
● Support Android Architecture Component
● Support Java
● Easy to use

7. Gradle config
koin_version = '1.0.0-beta-3'
// Koin Android ViewModel feature
implementation "org.koin:koin-android-viewmodel:$koin_version"
// Koin AndroidX ViewModel feature
implementation "org.koin:koin-androidx-viewmodel:$koin_version"
// Koin for Android
compile "org.koin:koin-android:$koin_version"

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

9. inject
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()
}
}

10. Start koin
class MyApplication : Application() {
override fun onCreate(){
super.onCreate()
// start Koin!
startKoin(this, listOf(myModule))
}
}

11. That’s it!

12. That’s it!
1. Define module
2. Inject Dependency
3. startKoin

13. Inject viewmodel
// declare ViewModel using the viewModel keyword
val myModule : Module = module {
viewModel { MyViewModel(get()) }
single { MyRepository() }
}

14. Inject viewmodel
class MyActivity() : AppCompatActivity() {
// lazy inject MyViewModel
val vm : MyViewModel by viewModel()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// or directly get
val vm : MyViewModel = getViewModel()
}
}

15. Inject viewmodel
class MyActivity() : AppCompatActivity() {
// lazy inject MyViewModel
val vm : MyViewModel by viewModel()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// or directly get
val vm : MyViewModel = getViewModel()
}
}

16. Type inference
class Controller(val service : BusinessService)
interface BusinessService {}
class LocalBusinessService() : BusinessService
val myModule = module {
factory { Controller(get()) }
single { LocalBusinessService() }
}

17. Type inference
class Controller(val service : BusinessService)
interface BusinessService {}
class LocalBusinessService() : BusinessService
val myModule = module {
factory { Controller(get()) }
single { LocalBusinessService() }
//crash!!
}

18. Type inference
class Controller(val service : BusinessService)
interface BusinessService {}
class LocalBusinessService() : BusinessService
val myModule = module {
factory { Controller(get()) }
single { LocalBusinessService() as BusinessService }
}

19. Type inference
class Controller(val service : BusinessService)
interface BusinessService {}
class LocalBusinessService() : BusinessService
val myModule = module {
factory { Controller(get()) }
single { LocalBusinessService() as BusinessService }
//or
single<BusinessService> { LocalBusinessService() }
}

20. What else?
Official Documentation:
https://beta.insert-koin.io/docs/1.0/documentatio
n/koin-core/index.html#_introduction

21. Bye Bye Dager~
https://medium.com/@charbgr/bye-bye-dagger-1494118dcd41

22. Dagger v.s. Koin
https://www.reddit.com/r/androiddev/comments/8ch4cg/dagger2_vs_koin_for_dependency_injection/

23. Q & A