Storing a boolean in an entity

[MaiTheLord]

I want to store a true boolean in an entity (something like "isUpgraded:1b" in NBT), but I am not sure whats the correct way to do that in forge. I wanted to use NBT, but I don't know how to read and write it in forge.
I saw that there's something called "Capabilities". it seems like it could be a better alternative, but I am not sure how to use it either.

What would be the better approach?

Edited July 4, 2022 by MaiTheLord

[warjort]

There are at least 2 different ways to do this.

 

net.minecraft.world.entity.ai.attributes.Attributes

This is not something I've not played with. So I can't say much about it.

The basic idea is each entity has a set of attributes. Which can also have permanent or transient AttributeModifiers. These modifiers are linked to ArmorItems or MobEffects, or they could be "ad hoc".

Forge has some events that let you configure attributes for entities: EntityAttribute(Creation/Modification)Event. Of course you need to register any custom attributes you make.

From what I can tell, these attributes are meant to be number ranges.

 

Forge's capabilities: https://forge.gemwire.uk/wiki/Capabilities

These are much more general and let you attach any data to most important in game things, but they also provide an "interface" for mod communication.

It is good to learn this system, things like item handling across mods or FE (forge energy) uses capabilities.

The major drawback with capabilities is they don't automatically synchronize with the client, so you have to do this yourself. Which is something people can struggle with until they understand it. The issue is due to capabilities being flexible, forge can't really know what/how/when you want to synchronize.

[MaiTheLord]

what about a raw NBT tag? I only need to store a boolean, after all

[warjort]

In game you just use a normal boolean field like normal in your capability class.

Its only if you want to send it across the network or save it you need to turn it into a ByteTag (there is no BooleanTag).

Wrapping it in a CompoundTag would future proof it, so you can add other data/tags later.

A plain byte tag is 1b, the compound tag gives it a name {name:1b} in future it might be {name:1b,another:"foobar"}

[MaiTheLord]

this exists:
 

CompoundTag tag = new CompoundTag();
        
tag.putBoolean("upgraded", true);

but how do I save it in an entity?

[warjort]

Click on the link above about capabilities and read it, in particular the attaching and the simple example at the end which has serialization.

[MaiTheLord]

I must be doing something wrong then.

 

CompoundTag tag = entity.serializeNBT();
tag.putBoolean("IsUpgraded", true);
entity.deserializeNBT(tag);

System.out.println(entity.serializeNBT().getBoolean("IsUpgraded")); // prints false

[MaiTheLord]

I did read it, and a capability seems like an overkill for what I want to do.

4 hours ago, warjort said:

Click on the link above about capabilities and read it, in particular the attaching and the simple example at the end which has serialization.

I might be wrong, but I think the person wanted me to look at this particular piece of code

        @Override
        public IntTag serializeNBT() {
            return backend.serializeNBT();
        }

        @Override
        public void deserializeNBT(IntTag tag) {
            backend.deserializeNBT(tag);
        }

 

Edited July 5, 2022 by MaiTheLord

[MaiTheLord]

I think I am doing something wrong.

https://gist.github.com/MaiTheLord/a19cf50de9735ce3a75fd3999fe82739

[MaiTheLord]

Thanks. that works. I need to sync it to the client though, as rendering depends on its value, and I have no idea how to implement that.

I should note that I am familiar with TCP packets, but never used packets with java or minecraft.

[warjort]

On that same wiki you used for capabilities you can read about networking. Here's the main page: https://forge.gemwire.uk/wiki/Main_Page

 

For your requirements, you need to use the PlayerEvent.StartTracking. This is fired when an entity comes into range of the player. Clients only see entities in range of the player.

When this event fires, you need to send your capability data to the player using a custom packet. The data would be entityId and your capability serialized as nbt.

On the client side you would find the entity (warning untested pseudo code)

LocalPlayer player = Minecraft.getInstance().player;
Level level = player.level;
Entity entity = level.getEntity(entityIdFromThePacket);

Then update your capability.

Additionally, if your capability data changes, you broadcast your packet to all players tracking the entity using the following distributor strategy 

PacketDistributor.TRACKING_ENTITY.with(() -> entity)

which sends the packet to all players tracking the entity.

 

For other explanations of these concepts see this recent thread.

It has a completely different synchronization requirement, so you won't be able to just copy the code.

https://forums.minecraftforge.net/topic/113225-1165-syncing-player-capabilities-to-client/

[warjort]

3 hours ago, diesieben07 said:

Note that you should not just use the same format as saving to disk for this. Only sync to the client what is necessary and if possible use a more compact format.

That is an optimisation that has its drawbacks.

Using the same code for network/disk serialization makes it easier/less error prone (you don't have to maintain 2 pieces of code that can get of step). You also don't have to worry about some method in your capability referencing data that is not there on the client.

Since capabilities are also meant for intermod communication, if another mod wants to use your capability for something else on the client, they may want a different bit of data that you are not sending. But then you can always say you don't support that on the client.

 

In this case, its not relevant since there is only one piece of data and its not meant to be used by other mods.