Scoping Dagger Components with ViewModels

ActivityScope.kt

@Scope
@Retention(AnnotationRetention.RUNTIME)
annotation class ActivityScope

build.gradle

dependencies {
    //other dependencies...
	
    implementation 'androidx.core:core-ktx:1.1.0'
    implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.1.0'
    implementation 'com.google.dagger:dagger:2.24'
    kapt 'com.google.dagger:dagger-compiler:2.24'
}

Functions.kt

abstract class ScopedComponent : ViewModel()

@MainThread
inline fun <reified C : ScopedComponent> AppCompatActivity.components(
    noinline ownerProducer: () -> ViewModelStoreOwner = { this },
    noinline factory: () -> C
) = viewModels<C> { viewModelFactoryOf { factory() } }

@MainThread
inline fun <reified VM : ViewModel> viewModelFactoryOf(
    noinline factory: () -> VM
) = object : ViewModelProvider.Factory {

    @Suppress("UNCHECKED_CAST")
    override fun <VM : ViewModel?> create(modelClass: Class<VM>): VM {
        return factory() as VM
    }
}

MainActivity.kt

class MainActivity: AppCompatActivity() {

    @Inject
    lateinit var mainPresenter: MainPresenter

    private val component: MainComponent by components {
        DaggerMainComponent.create()
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.main_activity)
        component.inject(this)
        mainPresenter.counter++
        findViewById<TextView>(R.id.message).text = mainPresenter.counter.toString()
    }
}

MainComponent.kt

@ActivityScope
@Component
abstract class MainComponent : ScopedComponent() {
    abstract fun inject(target: MainActivity)
}

MainPresenter.kt

@ActivityScope
class MainPresenter @Inject constructor(
    val mainRepository: MainRepository
) {
    var counter: Int = 0
}

MainRepository.kt

@Reusable
class MainRepository @Inject constructor()