creating a CoreComponent in core module

DaggerCoreComponent

import android.app.Application
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import dagger.Component
import dagger.Module
import javax.inject.Singleton

//these live in core module
@Module
object CoreModule {

}

@Singleton
@Component(modules = [CoreModule::class])
interface CoreComponent {

}

//these will be in feature module
@Module
object FeatureModule {

}

@FeatureScope
@Component(dependencies = [CoreComponent::class], modules = [FeatureModule::class])
interface FeatureComponent {
    fun inject(activity: FeatureActivity)
}

//created in app module
class App : Application() {

    lateinit var component: CoreComponent

    override fun onCreate() {
        super.onCreate()

        component = DaggerCoreComponent
            .builder()
            .build()
    }

}

class FeatureActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val appComponent = DaggerCoreComponent
            .builder()
            .build()

        DaggerFeatureComponent.Builder()
            .coreComponent(coreComponent)
            .build()
            .inject(this)
    }
}