====== Modify BlockEntity data ======

===== Introduction =====

Having a ''BlockEntity'', which holds some data, connected to a ''Block'' is nice, but how to change the data?

Before proceeding, you will need a [[tutorial:blocks|Block]] and a [[tutorial:blockentity|BlockEntity]], which should look similar to this:

<code java>
public class DemoBlockEntity extends BlockEntity {
 
    public int number = 0;
 
    public DemoBlockEntity(BlockPos pos, BlockState state) {
        super(ExampleMod.DEMO_BLOCK_ENTITY, pos, state);
    }
 
    @Override
    public void writeNbt(NbtCompound nbt) {
        nbt.putInt("number", number);
 
        super.writeNbt(nbt);
    }
    
    @Override
    public void readNbt(NbtCompound nbt) {
        super.readNbt(nbt);
 
        number = nbt.getInt("number");
    }
}
</code>

Make sure the ''number'' field is **public**, as we are going to change it in the ''DemoBlock'' class. You could also make getter and setter methods.

===== From Block's onUse() =====

This gets the ''BlockEntity'' at the right-clicked Block's position and if it's of the type ''DemoBlockEntity'', increments its ''number'' field and sends a chat message to the player.

<code java>
public class DemoBlock extends Block implements BlockEntityProvider {

    [...]

    @Override
    public ActionResult onUse(BlockState state, World world, BlockPos pos, PlayerEntity player, Hand hand, BlockHitResult hit) {
        if (!world.isClient){
            BlockEntity blockEntity = world.getBlockEntity(pos);
            if (blockEntity instanceof DemoBlockEntity){
                DemoBlockEntity demoBlockEntity = (DemoBlockEntity) blockEntity;
                demoBlockEntity.number++;
                player.sendMessage(Text.literal("Number is... "+demoBlockEntity.number), false);
                
                return ActionResult.SUCCESS;
            }
        }
        
        return ActionResult.PASS;
    }
}
</code>