Hello,

I'm trying to make an item, which has an inventory and save it through nbt data, but it doesn't seem to work at all.

Code:

https://github.com/harleybantonstratocaster/musicdiscsmod/tree/main/src/main

 

You can't store your inventory here: 

https://github.com/harleybantonstratocaster/musicdiscsmod/blob/72c6d49e0f167dd0d37724908d7521e28b6b647f/src/main/java/com/pnm/musicdiscsmod/item/PortableJukeboxItem.java#L24

There is only ever one instance of your item. You either store data in the ItemStack or a capability.

You seem to be setting up a capability.

But instead of actually using the capability, i.e. ItemStack.getCapability() you are using that single shared "inv" field instead.

Additionally here you are calling super() in your use method.

https://github.com/harleybantonstratocaster/musicdiscsmod/blob/72c6d49e0f167dd0d37724908d7521e28b6b647f/src/main/java/com/pnm/musicdiscsmod/item/PortableJukeboxItem.java#L39

This means it will return PASS as the result, i.e. you don't want to do anything.

Since this method is called first on the client that means the method is never invoked on the server.

You should use IteractionResultHandler.sidedSuccess(), see ThrowablePotionItem.use() for a simple example.