1.16.3 Trouble with capabilities

[link1213]

So I have been trying to make a capability and attach it to the player. This capability would monitor how much they are using the "drugs", which are just custom potions, in my mod and have negative consequences if they use them a lot. I have been following the documentation and guides but I still haven't managed to add the capability properly and I can't figure out why.

package com.mitymods.funwithdrugs.capabilities;

public interface IDrugUse
{
 public void remove(float points);
 public void add(float points);
 public void setDrugUse(float points);
 
 public float getDrugUse();
}

package com.mitymods.funwithdrugs.capabilities;

public class DrugUse implements IDrugUse 
{
	 
	private float drug_use;
	
	public DrugUse()
	{
		this.drug_use = 5;
	}

	@Override
	public void remove(float points)
	{
		// TODO Auto-generated method stub
		this.drug_use -= points;

	}

	@Override
	public void add(float points) {
		// TODO Auto-generated method stub
		this.drug_use += points;

	}

	@Override
	public void setDrugUse(float points) {
		// TODO Auto-generated method stub
		this.drug_use = points;

	}

	@Override
	public float getDrugUse() {
		// TODO Auto-generated method stub
		return this.drug_use;
	}

}

package com.mitymods.funwithdrugs.capabilities;

import net.minecraft.nbt.INBT;
import net.minecraft.util.Direction;
import net.minecraftforge.common.capabilities.Capability;
import net.minecraftforge.common.capabilities.CapabilityInject;
import net.minecraftforge.common.capabilities.ICapabilitySerializable;
import net.minecraftforge.common.util.LazyOptional;

public class DrugUseProvider implements ICapabilitySerializable<INBT>
{
	@CapabilityInject(IDrugUse.class)
	public static final Capability<IDrugUse> DRUG_USE_CAPABILITY = null;
	
	private LazyOptional<IDrugUse> instance = LazyOptional.of(DRUG_USE_CAPABILITY::getDefaultInstance);
	
	@Override
	public <T> LazyOptional<T> getCapability(Capability<T> cap, Direction side) {
		return cap == DRUG_USE_CAPABILITY ? instance.cast() : LazyOptional.empty();
	}

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

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

}

package com.mitymods.funwithdrugs.capabilities;

import net.minecraft.nbt.CompoundNBT;
import net.minecraft.nbt.INBT;
import net.minecraft.util.Direction;
import net.minecraftforge.common.capabilities.Capability;
import net.minecraftforge.common.capabilities.Capability.IStorage;

public class DrugUseStorage implements Capability.IStorage<IDrugUse>
{

	  @Override
	  public INBT writeNBT(Capability<IDrugUse> capability, IDrugUse instance, Direction side)
	  {
	    // return an NBT tag
		CompoundNBT tag = new CompoundNBT();
		tag.putFloat("drug_use", instance.getDrugUse());
		return tag;
	  }

	  @Override
	  public void readNBT(Capability<IDrugUse> capability, IDrugUse instance, Direction side, INBT nbt) {
	    // load from the NBT tag
		  CompoundNBT tag = (CompoundNBT) nbt;
		  instance.setDrugUse(tag.getFloat("drug_use"));
	  }

}

package com.mitymods.funwithdrugs.events;

import com.mitymods.funwithdrugs.FunWithDrugs;
import com.mitymods.funwithdrugs.capabilities.DrugUseProvider;
import com.mitymods.funwithdrugs.capabilities.IDrugUse;

import net.minecraft.entity.Entity;
import net.minecraft.entity.player.PlayerEntity;
import net.minecraft.util.ResourceLocation;
import net.minecraftforge.common.util.LazyOptional;
import net.minecraftforge.event.AttachCapabilitiesEvent;
import net.minecraftforge.event.entity.living.LivingFallEvent;
import net.minecraftforge.eventbus.api.SubscribeEvent;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.common.Mod.EventBusSubscriber.Bus;

@Mod.EventBusSubscriber(modid = FunWithDrugs.MOD_ID, bus = Bus.FORGE)
public class AddDrugUse 
{
	  @SubscribeEvent
		public static void onAttachCapabilities(AttachCapabilitiesEvent<Entity> event)
	  {
			if (event.getObject() instanceof PlayerEntity)
			{
				event.addCapability(new ResourceLocation(FunWithDrugs.MOD_ID, "drug_use"), new DrugUseProvider());
			}
			
	  }
	  
	  @SubscribeEvent
	  public void onPlayerFalls(LivingFallEvent event)
	  {
		  
		  if(event.getEntityLiving() instanceof PlayerEntity)
		  {
			  PlayerEntity player = (PlayerEntity) event.getEntityLiving();
			  IDrugUse drugUse = player.getCapability(DrugUseProvider.DRUG_USE_CAPABILITY, null);
			  if (drugUse.getDrugUse() == 5)
			  {
				  player.setHealth(0);
				  
			  }
		  }

	  }

}

And a bit of code in my main mod file

FMLJavaModLoadingContext.get().getModEventBus().addListener(this::onCommonSetup);

  private void onCommonSetup(FMLCommonSetupEvent event)
    {
    	CapabilityManager.INSTANCE.register(IDrugUse.class, new DrugUseStorage(), DrugUse::new);	
    }

 

The purpose of this second event is to test if the player has the capability and if it equals the default value, however this code doesn't even work for some reason that I can not figure out. I am very stumped on what the issue is. And I DO know java, I just am having a hard time understanding this specific thing.

 

I know my code is probably pretty messy, I do intend to clean it up once I can figure out what I'm doing wrong

[diesieben07]

45 minutes ago, link1213 said:

IDrugUse drugUse = player.getCapability(DrugUseProvider.DRUG_USE_CAPABILITY, null);

This should not even compile, considering getCapability returns a LazyOptional, not an IDrugUse.

[link1213]

58 minutes ago, diesieben07 said:

This should not even compile, considering getCapability returns a LazyOptional, not an IDrugUse.

Ah It complied earlier but i just checked and it didn't this time so I must have accidentally changed something before I posted the code here. So how would I want to go about this then? Would I just want to cast the LazyOptional to an IDrugUse? Or is the issue a lot more complex?

[diesieben07]

Just now, link1213 said:

Would I just want to cast the LazyOptional to an IDrugUse?

This shows a fundamental lack of knowledge about casting and inheritance in Java. Please learn the basics before modding.

[link1213]

I do know the basics. I have taken 3 college courses on java. What I do not understand is what a LazyOptional is which is why I am so confused. I know exactly how inheritance and casting works, but since I dont get what a LazyOptional is, I do not know if it works in this situation. Hence why I asked the question if that Is what I am to do. I also asked that question as that is the suggestion that Eclipse gave me to solve it so it wasnt a question that I asked out of nowhere.

Edited October 20, 2020 by link1213

[link1213]

I am grateful for your help so sorry if that last statement sounded rude, I just don't get why you assume that me having trouble = me not knowing java

[diesieben07]

A LazyOptional is a class.

With great Javadocs. Read it and you shall learn what it is, that's why Javadocs exist.

[Draco18s]

 

[link1213]

So then if i am understanding this correctly, LazyOptional is holding a value, and in this case that value is an instance of my DrugUse capability. So when I am calling the getCapability function, I am getting the LazyOptional that contains that players DrugUse Capability? So I would somehow need to get that info, from the LazyOptional if I wanted to check it for anything?

[diesieben07]

Just now, link1213 said:

So I would somehow need to get that info, from the LazyOptional if I wanted to check it for anything?

Correct, there are various methods that let you do that.

[link1213]

So I think I have figured it out, i tested it with a couple events and while It is having no issue getting the data, it seems to have a problem checking it.

  @SubscribeEvent
	    public static void onPlayerLogsIn(PlayerLoggedInEvent event)
	  {
	        PlayerEntity player = event.getPlayer();
	        LazyOptional<IDrugUse> drugUse = player.getCapability(DrugUseProvider.DRUG_USE_CAPABILITY, null);
			IDrugUse pDrugUse = drugUse.orElse(new DrugUse());
			 player.sendMessage(new StringTextComponent("Your drug use variable is " + (pDrugUse.getDrugUse())), null);
	  }

This does display the correct number

	  @SubscribeEvent
	  public void onPlayerDamage(LivingDamageEvent event)
	  {
		  
		  if(event.getEntityLiving() instanceof PlayerEntity)
		  {
			  PlayerEntity player = (PlayerEntity) event.getEntityLiving();
			  LazyOptional<IDrugUse> drugUse = player.getCapability(DrugUseProvider.DRUG_USE_CAPABILITY, null);
			  IDrugUse pDrugUse = drugUse.orElse(new DrugUse());
			  if (pDrugUse.getDrugUse() == 5)
			  {
				  player.setHealth(0);
				  
			  }
		  }

	  }

This does nothing however. Am I accessing the data incorrectly? 

Edited October 20, 2020 by link1213

[poopoodice]

You should throw an exception if the player does not have the capability because what you do here 

drugUse.orElse(new DrugUse())

is pointless because if the player does not have the capability you are always accessing data of a new instance of your capability.

Also is the event correctly registered?

Edited October 20, 2020 by poopoodice

[diesieben07]

5 minutes ago, link1213 said:

IDrugUse pDrugUse = drugUse.orElse(new DrugUse());

Is this really what you want? Please think about what it means if the capability is not there and what you want to do in that case (can that even happen?). 

[link1213]

4 minutes ago, diesieben07 said:

Is this really what you want? Please think about what it means if the capability is not there and what you want to do in that case (can that even happen?). 

Shouldn't every player have the capability regardless by doing 

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

So if somehow the player doesn't have the capability, wouldn't the orElse method give it to them? I wouldn't want there to be a situation where the player does not have the capability

Edited October 20, 2020 by link1213

[diesieben07]

Just now, link1213 said:

So if somehow the player doesn't have the capability, wouldn't the orElse method give it to them?

No, it would not. It would simply create a temporary object.

 

1 minute ago, link1213 said:

Shouldn't every player have the capability regardless by doing 

Correct.

 

1 minute ago, link1213 said:

I wouldn't want there to be a situation where the player does not have the capability

Correct. So what do you do in Java when you are in a wrong situation? You throw an exception. In this case, you can use orElseThrow for this.

[Draco18s]

or use ifPresent

[diesieben07]

11 hours ago, Draco18s said:

or use ifPresent

Which goes in the same direction of sweeping the problem (capability not present) under the rug.

[Draco18s]

2 hours ago, diesieben07 said:

Which goes in the same direction of sweeping the problem (capability not present) under the rug.

It depends on the use-case

[diesieben07]

2 minutes ago, Draco18s said:

It depends on the use-case

Correct. Read the rest of the thread