Parameterised reactive use cases in Kotlin

GetPosts.kt

class GetPosts @Inject constructor(
        uiExecutor: UiExecutor,
        @Named("ioExecutor") backgroundExecutor: BackgroundExecutor,
        private val redditRepository: RedditRepository
) : ReactiveUseCase<List<RedditLink>>(uiExecutor, backgroundExecutor) {

    fun execute(onNext: (List<RedditLink>) -> Unit,
                onError: (Throwable) -> Unit,
                onCompleted: () -> Unit) {
        super.executeUseCase(onNext, onError, onCompleted)
    }

    override fun useCaseObservable(): Observable<List<RedditLink>> {
        val subreddit = Subreddit.ANDROIDDEV
        val filterType = RedditFilterType.HOT
        return redditRepository.getLinksForSubreddit(subreddit, filterType)
    }
}

MainActivity.kt

getPosts.execute(
        onNext = { it.forEach { Log.d("darren", it.selftext) } },
        onError = { Log.d("darren", it.message )},
        onCompleted = { Log.d("darren", "onCompleted") }
)

ReactiveUseCase.kt

abstract class ReactiveUseCase<ObservableType> (
        private val uiExecutor: UiExecutor,
        private val backgroundExecutor: BackgroundExecutor) {

    private var subscription = Subscriptions.empty()

    protected fun executeUseCase(onNext: (ObservableType) -> Unit = {},
                                 onError: (Throwable) -> Unit = {},
                                 onCompleted: () -> Unit = {}) {
        this.subscription = useCaseObservable()
                .subscribeOn(backgroundExecutor.scheduler)
                .observeOn(uiExecutor.scheduler)
                .subscribe(onNext, onError, onCompleted)
    }

    protected abstract fun useCaseObservable(): Observable<ObservableType>

    fun unsubscribe() {
        if (!subscription.isUnsubscribed) {
            subscription.unsubscribe()
        }
    }
}