[SOLVED] [1.12.2] world is null when reading NBT

[scrouthtv]

Hello. I am currently writing a mod which includes pipes.

My pipes have a tree-like structure, with one root node to which all pipes directly point. The root node saves all data (which pipes are connected, which machines are adjacent, ...)

To save the current state of the pipes and keep it even when reopening the world, I saved all the data to an NBT tag:

@Nonnull
@Override
public NBTTagCompound writeToNBT(@Nonnull final NBTTagCompound compound) {
    if (!world.isRemote) {
		if (network != null) {
			NBTTagCompound networkTag = new NBTTagCompound();
			networkTag.setTag("root", NBTHelper.writeBlockPosToTag(network.getRoot().getPos()));
			if (this.equals(network.getRoot())) {
				networkTag.setTag("data", network.rootCompound());
			}
			compound.setTag("network", networkTag);
			System.out.println("wrote " + compound);
		}
	}
	return super.writeToNBT(compound);
}

Which works:

wrote {network:{data:{moduleList:[],pipeList:[{a:{x:194,y:64,z:167},b:{x:194,y:64,z:168}},{a:{x:194,y:64,z:168},b:{x:194,y:64,z:169}}]},root:{x:194,y:64,z:167}}}

 

Now I want to read this data and re-create the network:

@Override
public void readFromNBT(@Nonnull final NBTTagCompound compound) {
	if (!world.isRemote()) {
		if (compound.hasKey("network")) {
			System.out.println("read " + compound);
			NBTTagCompound networkTag = compound.getCompoundTag("network");
			NBTTagCompound networkRootTag = networkTag.getCompoundTag("root");
          
			BlockPos rootPos = NBTHelper.readTagToBlockPos(networkRootTag);
			TileEntity root = world.getTileEntity(rootPos);
          
          	// ...

		}
		super.readFromNBT(compound);
	}
}

 

However, this throws an NPE because world seems to be null when the nbt is read. I also tried those methods:

System.out.println(getWorld() == null); // true
System.out.println(world == null); // true
System.out.println(Minecraft.getMinecraft().world == null); // true
System.out.println(FMLClientHandler.instance().getWorldClient() == null); // true and should be for client only anyways

 

My first idea to fix this was to override setWorld() and call the readFromNBT method when the world is set, but that seems a bit weird. What am I missing?

 

Thanks for any help in advance

[scrouthtv]

Okay, so as I just found out there is a TileEntity#create(World, NBTTagCompound) static method which should do what I want.

 

But how do override it? How do I make my TE class known to the create method?

[Novârch]

8 minutes ago, scrouthtv said:

But how do override it?

You cannot override static methods, that is basic Java, it doesn't make any sense.

[scrouthtv]

That's the reason I asked

[Novârch]

3 minutes ago, scrouthtv said:

That's the reason I asked

That method cannot be what you're looking for, it's static and you can't override static methods, look for another method.

Edited July 13, 2020 by Novârch

[scrouthtv]

Okay I halfway fixed it:

 

The method is exactly what I'm looking for. I just don't have to override, but use it. It reads the id from the nbt data and instantiates a new TileEntity with the id as ResourceLocation. 

 

net.minecraft.tileentity.TileEntity:

@Nullable
public static TileEntity create(World worldIn, NBTTagCompound compound) {
	String s = compound.getString("id");
	Class <? extends TileEntity > oclass = null;
	oclass = (Class)REGISTRY.getObject(new ResourceLocation(s));
	tileentity = oclass.newInstance();
	// ...
	tileentity.setWorldCreate(worldIn);
	tileentity.readFromNBT(compound);
	// ...
	return tileentity;
}

 

The only thing I still have to do is figure out what #setWorldCreate means, since there is 0 documentation on it.

 

I think I will simply override setWorldCreate in my TE and use that world to do everything.

Edited July 13, 2020 by scrouthtv

[DavidM]

You are not supposed to access the World in readFromNBT. The world is can be uninitialized at that time.

Like the name suggests, you should only read data from NBT during that time.

If you want to get another tile entity during initialization, you can make it a lazy value and initialize (when first used/first tick in world depending on how you want to use it) based on the BlockPos (which is read from NBT).

Edited July 13, 2020 by DavidM