I have been working on a mod that has random disease events that periodically infect players. To store what disease a player has, I have tried creating a Capability. I do know Java but I am fairly new to 1.16.5 (just updated from 1.17.10 a week ago!). Looking at the EnergyStorage forge code and a couple of other topics on this forum, I have coded a Capability with only one error in the AttachCapabilitiesEvent when I run my mod. I have searched in the forge documentation and on this forum for a couple of days but haven't been able to find anything. Here s my code.

IDiseases:

public interface IDiseases {
    int getDiseases();
    
    void setDiseases(int i);
}

Diseases:

public class Diseases implements IDiseases{

	private int diseases;
	
	public Diseases() {
		setDiseases(0);
	}
	
	@Override
	public int getDiseases() {
		return diseases;
	}

	@Override
	public void setDiseases(int i) {
		diseases = i;
	}

}

DiseasesStorage:

public class DiseasesStorage implements IStorage<IDiseases>{

	@Override
	public INBT writeNBT(Capability<IDiseases> capability, IDiseases instance, Direction side) {
		CompoundNBT tag = new CompoundNBT();
		tag.putInt("diseases", instance.getDiseases());
		return tag;
	}

	@Override
	public void readNBT(Capability<IDiseases> capability, IDiseases instance, Direction side, INBT nbt) {
		CompoundNBT tag = new CompoundNBT();
		instance.setDiseases(tag.getInt("diseases"));
	}

}

DiseasesProvider:

public class DiseasesProvider implements ICapabilitySerializable<INBT> {

	@CapabilityInject(IDiseases.class)
	public static final Capability<IDiseases> DISEASES_CAPABILITY = null;

	private LazyOptional<IDiseases> instance = LazyOptional.of(DISEASES_CAPABILITY::getDefaultInstance);

	@Override
	public <T> LazyOptional<T> getCapability(Capability<T> cap, Direction side) {
		return cap == DISEASES_CAPABILITY ? instance.cast() : LazyOptional.empty();
	}

	@Override
	public INBT serializeNBT() {
		return DISEASES_CAPABILITY.getStorage().writeNBT(DISEASES_CAPABILITY, this.instance.orElseThrow(() -> new IllegalArgumentException("LazyOptional must not be empty!")), null);
	}

	@Override
	public void deserializeNBT(INBT nbt) {
		DISEASES_CAPABILITY.getStorage().readNBT(DISEASES_CAPABILITY, this.instance.orElseThrow(() -> new IllegalArgumentException("LazyOptional must not be empty!")), null, nbt);
	}

}

Epidemics (Main Class):

@Mod("epidemics")
@Mod.EventBusSubscriber(modid = Epidemics.MOD_ID, bus = Bus.MOD)
public class Epidemics {

	public static final Logger LOGGER = LogManager.getLogger();
	public static final String MOD_ID = "epidemics";

	public Epidemics() {
		IEventBus bus = FMLJavaModLoadingContext.get().getModEventBus();
		
		BlockInit.BLOCKS.register(bus);
		ItemInit.ITEMS.register(bus);
		EffectsInit.EFFECTS.register(bus);
		SymptomInit.SYMPTOMS.register(bus);
		SoundInit.SOUNDS.register(bus);
		
		MinecraftForge.EVENT_BUS.register(this);
		FMLJavaModLoadingContext.get().getModEventBus().addListener(Epidemics::onCommonSetup);
	}

	@SubscribeEvent
	public static void onRegisterItems(final RegistryEvent.Register<Item> event) {
		BlockInit.BLOCKS.getEntries().stream().map(RegistryObject::get).forEach(block -> {
			event.getRegistry().register(new BlockItem(block, new Item.Properties().tab(ItemGroup.TAB_MISC)).setRegistryName(block.getRegistryName()));
		});
	}
	
	
	@SubscribeEvent
	public static void onCommonSetup(FMLCommonSetupEvent event) {
		CapabilityManager.INSTANCE.register(IDiseases.class, new DiseasesStorage(), Diseases::new);
	}

	@SubscribeEvent
	public static void onAttachCapabilities(AttachCapabilitiesEvent<Entity> event) {
		if (event.getObject() instanceof PlayerEntity) {
			event.addCapability(new ResourceLocation(Epidemics.MOD_ID, "diseases"), new DiseasesProvider());
		}
	}
}

The error:

[19:31:23] [modloading-worker-2/DEBUG] [ne.mi.fm.AutomaticEventSubscriber/LOADING]: Attempting to inject @EventBusSubscriber classes into the eventbus for epidemics
[19:31:23] [modloading-worker-2/DEBUG] [ne.mi.fm.AutomaticEventSubscriber/LOADING]: Auto-subscribing com.monkey.epidemics.Epidemics to MOD
[19:31:23] [modloading-worker-2/ERROR] [ne.mi.fm.ja.FMLModContainer/LOADING]: Failed to register automatic subscribers. ModID: epidemics, class com.monkey.epidemics.Epidemics
java.lang.IllegalArgumentException: Method public static void com.monkey.epidemics.Epidemics.onAttachCapabilities(net.minecraftforge.event.AttachCapabilitiesEvent) has @SubscribeEvent annotation, but takes an argument that is not a subtype of the base type interface net.minecraftforge.fml.event.lifecycle.IModBusEvent: class net.minecraftforge.event.AttachCapabilitiesEvent
	at net.minecraftforge.eventbus.EventBus.registerListener(EventBus.java:145) ~[eventbus-4.0.0.jar:?] {}
	at net.minecraftforge.eventbus.EventBus.lambda$registerClass$2(EventBus.java:78) ~[eventbus-4.0.0.jar:?] {}
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184) ~[?:1.8.0_291] {}
	at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175) ~[?:1.8.0_291] {}
	at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175) ~[?:1.8.0_291] {}
	at java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948) ~[?:1.8.0_291] {}
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482) ~[?:1.8.0_291] {}
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472) ~[?:1.8.0_291] {}
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151) ~[?:1.8.0_291] {}
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174) ~[?:1.8.0_291] {}
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[?:1.8.0_291] {}
	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418) ~[?:1.8.0_291] {}
	at net.minecraftforge.eventbus.EventBus.registerClass(EventBus.java:78) ~[eventbus-4.0.0.jar:?] {}
	at net.minecraftforge.eventbus.EventBus.register(EventBus.java:118) ~[eventbus-4.0.0.jar:?] {}
	at net.minecraftforge.fml.AutomaticEventSubscriber.lambda$inject$6(AutomaticEventSubscriber.java:75) ~[forge:?] {re:classloading}
	at java.util.ArrayList.forEach(ArrayList.java:1259) ~[?:1.8.0_291] {}
	at net.minecraftforge.fml.AutomaticEventSubscriber.inject(AutomaticEventSubscriber.java:62) ~[forge:?] {re:classloading}
	at net.minecraftforge.fml.javafmlmod.FMLModContainer.constructMod(FMLModContainer.java:91) ~[forge:36.1] {re:classloading}
	at net.minecraftforge.fml.ModContainer.lambda$buildTransitionHandler$4(ModContainer.java:120) ~[forge:?] {re:classloading}
	at java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1640) [?:1.8.0_291] {}
	at java.util.concurrent.CompletableFuture$AsyncRun.exec(CompletableFuture.java:1632) [?:1.8.0_291] {}
	at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289) [?:1.8.0_291] {}
	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1067) [?:1.8.0_291] {}
	at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1703) [?:1.8.0_291] {}
	at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:172) [?:1.8.0_291] {}

I am still relatively new to 1.16.5 so Capabilities are still new and scary to me. I know I messed up the arguments somewhere but can't quite find it.

Edited May 1, 20214 yr by MonkeyKnight
Solved

You've subscribed to the wrong event bus.

Thank you! That did the trick.