[1.16.5] Write/read custom class to/from NBT

[J3ramy]

Hey guys,

I am trying to save a custom class in my tile entity`s NBT data.

I think I figured out how to save it, but I don't know how to load it.

 

Ingame Server class (Class that should be saved to nbt)

Spoiler

public class Server implements INBTSerializable {

    public enum ServerType{
        CUSTOM
    }

    private boolean isOn = false;
    private ServerType serverType;
    private String ip;
    private BlockPos pos;
    private Database db;

    public Server(ServerType serverType, String ip, BlockPos pos, Database db){
        this.serverType = serverType;
        this.ip = ip;
        this.pos = pos;
        this.db = db;
    }
  
    @Override
    public INBT serializeNBT() {
        CompoundNBT nbt = new CompoundNBT();

        nbt.putBoolean("isOn", this.isOn);
        nbt.putInt("serverType", this.serverType.ordinal());
        nbt.putString("ip", this.ip);
        nbt.put("pos", NBTUtil.writeBlockPos(this.pos));
        nbt.put("db", this.db.serializeNBT());

        return nbt;
    }

    @Override
    public void deserializeNBT(INBT compound) {
        CompoundNBT nbt = (CompoundNBT) compound;

        this.isOn = nbt.getBoolean("isOn");
        this.serverType = ServerType.values()[nbt.getInt("")];
        this.ip = nbt.getString("name");
        this.pos = NBTUtil.readBlockPos(nbt);
        this.db = (Database) nbt.get("db");
    }

 

 

My tile entity class

Spoiler

public class ServerTile extends TileEntity {

    private Server server;

    public ServerTile(TileEntityType<?> tileEntityType) {
        super(tileEntityType);
    }

    public ServerTile(){
        this(ModTileEntities.SERVER_TILE.get());
    }


    @Override
    public void read(BlockState state, CompoundNBT nbt) {

        this.server = ...

        super.read(state, nbt);
    }

    @Override
    public CompoundNBT write(CompoundNBT nbt) {
        nbt.put("server", this.server.serializeNBT());

        return super.write(nbt);
    }

 

 

Thanks for your help

[Luis_ST]

you can create a constructor with a CompoundNBT as parameter, inside the constructor you read the data and set the fields
in this case your fields can be final (if you want that they are), then you can simply create a new instance
the other option would be to add an empty constructor and then call Server#serializeNBT

i personally prefer the first option but you could choose the option you want
i would also recommend you to specify the INBT type in the type arguments of INBTSerializable

last but not least i would recommend you to update to 1.18 since 1.16.5 will fall out of support in the next 2-3 days

Edited July 5, 2022 by Luis_ST

[J3ramy]

Quote

This doesn't look right.

Thanks. I forgot to add the key ^^

 

Quote

INBTSerializable only really works if you have a no-argument constructor, so you can create the instance. I would recommend to instead make a static factory method and not use INBTSerializable.

Do you have an example?

[Luis_ST]

5 minutes ago, J3ramy said:

Do you have an example?

Spoiler

	public void save() {
		Foo foo = new Foo(10);
		CompoundTag tag = foo.serializeNBT();
		// do stuff
	}
	
	public void load(CompoundTag tag) {
		Foo foo = new Foo();
		foo.deserializeNBT(tag);
	}
	
	public class Foo implements INBTSerializable<CompoundTag> {
		
		protected int data;
		
		public Foo() {
			
		}
		
		public Foo(int data) {
			this.data = data;
		}
		
		@Override
		public CompoundTag serializeNBT() {
			CompoundTag tag = new CompoundTag();
			tag.putInt("data", this.data);
			return tag;
		}

		@Override
		public void deserializeNBT(CompoundTag tag) {
			this.data = tag.getInt("data");
		}
		
	}

this is a simply example, but i would recommend to use a factory method or a constructor instead

Note: create with mojang mappings

[J3ramy]

Thank you.

 

I decided for the constructor way and changed the class to

Spoiler

public class Server {

    public enum ServerType{
        CUSTOM
    }

    private boolean isOn = false;
    private boolean isSet = false;
    private final ServerType serverType;
    private final String ip;
    private final BlockPos pos;
    private final Database db;

    public Server(CompoundNBT nbt){
        this.isOn = nbt.getBoolean("isOn");
        this.isSet = nbt.getBoolean("isSet");
        this.serverType = ServerType.valueOf(nbt.getString("serverType"));
        this.ip = nbt.getString("name");
        this.pos = NBTUtil.readBlockPos(nbt);
        this.db = (Database) nbt.get("db");
    }

}

 

But how am I supposed to save/load this in the tile entity write and read method?

 

EDIT:

I created a getData method in Server which returns a CompoundNBT containing the class data.

Now, I do this in my tile entity:

Spoiler

 @Override
    public void read(BlockState state, CompoundNBT nbt) {

        this.server = new Server(nbt);

        super.read(state, nbt);
    }

    @Override
    public CompoundNBT write(CompoundNBT nbt) {

        nbt.put("server", this.server.getData());

        return super.write(nbt);
    }

 

 

Edited July 5, 2022 by J3ramy

[warjort]

   public void read(BlockState state, CompoundNBT nbt) {

        this.server = new Server(nbt.getCompound("server");

        super.read(state, nbt);
    }

You need to retrieve the subtag of the tile's nbt. The place where you put it.

 

The read/write happens automatically. Except, if you change data for the tile, you need to call setChanged() so minecraft knows it needs to save it.

Edited July 5, 2022 by warjort

[warjort]

Quote

Except, if you change data for the tile, you need to call setChanged() so minecraft knows it needs to save it.

This also notifies neighbouring blocks they may need to do stuff.

e.g. if you output a redstone signal any redstone would recalculate its signal strength.

Edited July 5, 2022 by warjort

[J3ramy]

Nice thank you. It works now!