Events - GregHib/void GitHub Wiki

All of Void's content is built using Events to transmit information between entities and content in handlers.

Whilst conceptually it can be considered as a Publish-Subscriber model since 2.3.0 Void does not have a concept of an Event class due to performance and overhead reasons. Instead on startup scripts store functions which are then called directly when "emitting" an event.

The simplest example would be the Spawn "event".

interface Spawn {
    fun playerSpawn(handler: Player.() -> Unit) {
        playerSpawns.add(handler)
    }
    
    companion object : AutoCloseable {
        private val playerSpawns = mutableListOf<(Player) -> Unit>()
        
        fun player(player: Player) {
            for (handler in playerSpawns) {
                handler(player)
            }
        }
    }
}

It registers it's subscription inside a script:

class HelloWorld : Spawn {
    init {
        playerSpawn {
            message("Welcome to Void.")
        }
    }
}

And can be emitted by calling: Spawn.player(myPlayer).

Script interfaces are often added to Script.kt to simplify imports and accessing them inside of scripts, although whilst not required all external events must still be AutoCloseable and be added to Script.kt's interfaces list.