Event.kt

package xyz.mackan.rpggame.events

interface Event {
    val eventName: String
}

data class GameObjectSelectEvent(val instanceId: Int): Event {
    override val eventName: String = "GameObjectSelectEvent"

    companion object : Event {
        override val eventName: String = "GameObjectSelectEvent"
    }
}

data class GameObjectDeselectEvent(val instanceId: Int): Event {
    override val eventName: String = "GameObjectDeselectEvent"

    companion object : Event {
        override val eventName: String = "GameObjectDeselectEvent"
    }
}

EventEmitter.kt

package xyz.mackan.rpggame.events


open class EventEmitter {
    var handlerMap = mutableMapOf<String, MutableList<(Any) -> Unit>>()

    /**
     * Adds the [handler] to the subscribers for the event [event]
     */
    fun <T : Event> on (event: Event, handler: (T) -> Unit) {
        handlerMap.putIfAbsent(event.eventName, mutableListOf<(T: Any) -> Unit>())

        handlerMap[event.eventName]!!.add(handler as (Any) -> Unit)
    }

    /**
     * Emits the [event] to it's subscribers
     */
    fun <T: Event> emit (event: T) {
        if (!handlerMap.containsKey(event.eventName)) return

        for (subscriber in handlerMap[event.eventName]!!) {
            subscriber(event)
        }
    }
}

Manager.kt

package xyz.mackan.rpggame

import com.badlogic.gdx.InputProcessor
import com.badlogic.gdx.math.Vector3
import cookiedragon.eventsystem.EventDispatcher
import xyz.mackan.rpggame.events.*
import xyz.mackan.rpggame.utils.GameObject

class Manager : EventEmitter() {
	init {
		this.on<GameObjectSelectEvent>(GameObjectSelectEvent) {
			println("Selected ${it.instanceId}")
		}
	}
	
	fun doEmit () {
		this.emit(GameObjectSelectEvent(1))
	}
}