Listeners

• Listeners use accessors like Queries, but are not iterators.
• Instead, they define handlers which run when an event has been called on an entity that matches the requested data.

Creating a listener

As usual, extend GearyListener and add accessors:

class ExplosionBehaviour : GearyListener() {
    private val ResultScope.explosionData by get<Explosion>()
...

Add handlers

Handlers are added by overriding the GearyHandlerScope.init() function.

This function gets called on any matched archetype. It contains info regarding that archetype as well as extension functions to make listening to events easier.

You may use on<EventType>{ event -> ... } to create a new handler. This handler puts you in a ResultScope and passes along an event: EventType.

Search for extension functions before using this function, since you may accidentally use events that are not handled in Geary at all (ex regular Bukkit events.)

Here's a potential example from Minecraft:

...

    override fun GearyHandlerScope.init() {
        onItemLeftClick { event ->
            event.player.location.explode(explosionData)
        }
    }
}

Useful events

• onComponentAdd - Fires as soon as all requested components are present on an entity.

• onComponentRemove - Not yet implemented, but will be similar.

• ItemActions - Contains many item-related ones provided by Looty.

• More related with Bukkit events to come...