Dispatcher.kt

interface Subscriber<in T> {
    fun onNext(data: T)
}

abstract class Dispatcher<T> {
    private val subscriptions = ArrayList<Subscriber<T>>()

    fun subscribe(subscriber: Subscriber<T>): Boolean =
            subscriptions.add(subscriber)

    fun unsubscribe(subscriber: Subscriber<T>): Boolean =
            subscriptions.remove(subscriber)

   // Other functions you want to have like size, unsubscribeAll, etc.

    open fun dispatch(data: T) =
            subscriptions.forEach { it.onNext(data) }

    fun isSubscribed(subscriber: Subscriber<T>): Boolean {
        return subscriptions.any { it == subscriber }
    }
}