Events

Commander introduces a new data pack event system, which allows data packs to listen to events just like mods.

The best practice is to have a generic Fabric event and register Commander as one of its listeners.

Creating event types

To implement event support for your mod you must first register an event type for Commander to dispatch. You can build and register events with the EventType.Builder class.

public static final EventType CUSTOM_EVENT = EventType.builder().build(new Identifier("modid", "custom_event"));

If your event requires a return type, you can specify a cancel term codec with cancelTerm().

EventType.builder()
    .cancelTerm(Codec.INT)
    .build(new Identifier("modid", "custom_event"));

Events can accept additional parameters using extension(). After specifying an extension you can return a custom type.

EventType.builder()
    .extension(Codec.STRING, subscriptions -> {
        //handle data.
        return /*Return listeners*/;
    })
    .build(new Identifier("modid", "custom_event"));

The default return type is List<Command.Conditioned>.

Invoking the event

If you didn't specify an extension, or opted to return a List<Command.Conditioned>, you can use the included EventExecutors util.

To use the util, you have to pass the event type, the execution world, and a loot context supplier.

CustomEvent.EVENT.register((world, entity) -> runVoid(CUSTOM_EVENT, world, () -> makeContext(world, entity, entity.getPos())));

private static LootContext makeContext(ServerWorld world, Entity entity, Vec3d origin) {
    LootContextParameterSet.Builder builder = new LootContextParameterSet.Builder(world);
    builder.add(THIS_ENTITY, entity).add(ORIGIN, origin);
    return new LootContext.Builder(builder.build(LootContextTypes.COMMAND)).build(null /*Optional.empty() in 1.20.4*/);
}

If you did specify an extension, or are using an unsupported return type, you'll have to write custom resolution logic.

To do that you'll simply have to create an EventContext. EventContext is used to pass execution parameters to commands.

EventContext context = EventContext.builder(type)
        .addParameter(EventKey.LOOT_CONTEXT, /*instance of loot context*/)
        .build();
for (Command.Conditioned subscriber : subscribers) subscriber.execute(context);

To get the return value, you can call getReturnValue(def), the default value can be null. The return type is generic.

boolean val = context.getReturnValue(def);
if (val != def) return val;