[Question] what is the UUID for with attributes on items?

[theishiopian]

I am attempting to make a weapon with a custom attribute, in this case armor penetration. Everything has made sense so far, except that the attribute map on the item requires a UUID, which from what i can tell, is just preset at random. 

My current constructor looks like this:

public WeaponMace(IItemTier tier, Properties properties, float baseDamage, double speed, int armorPen)
    {
        super(tier, properties);

        Builder<Attribute, AttributeModifier> builder = ImmutableMultimap.builder();
        float attackDamage = baseDamage + tier.getAttackDamageBonus();
        builder.put(Attributes.ATTACK_DAMAGE, new AttributeModifier(BASE_ATTACK_DAMAGE_UUID, "Weapon modifier", attackDamage, AttributeModifier.Operation.ADDITION));
        builder.put(Attributes.ATTACK_SPEED, new AttributeModifier(BASE_ATTACK_SPEED_UUID, "Weapon modifier", speed, AttributeModifier.Operation.ADDITION));
        builder.put(ModAttributes.ARMOR_PENETRATION.get(), new AttributeModifier(UUID.fromString("c7675e5c-2e25-4589-ace1-f0ad816b40b8"), "Weapon modifier", armorPen, AttributeModifier.Operation.ADDITION));
        this.defaultModifiers = builder.build();
    }

Is this an ok way of doing this? 

[vemerion]

1 hour ago, theishiopian said:

Everything has made sense so far, except that the attribute map on the item requires a UUID, which from what i can tell, is just preset at random.

The UUID is used to identify the attribute. This means that if two items have the same UUID for an attribute, the most recently equipped one will override the other if both are equipped at the same time. The Minecraft wiki has some info about it on the attribute page here. What I usually do is generate a random UUID once with UUID.randomUUID(), and then use that in UUID.fromString().