What do userdatas actually store?

[au_tk]

I’ve scoured the devforum for information on userdatas repeatedly. There is almost nothing on what they actually do. Most threads usually just talk about the metatables that come attached to a userdata when you do newproxy(true). Ok, cool, but it’s nothing I couldn’t do with some tables and metatables on their own.

I learned that userdatas can be used for absolute security, completely unmodifiable values:

@IdiomicLanguage

Because userdata’s don’t store keys/values, rawset and rawget don’t affect them. With a locked metatable, you have absolute control and security. __index will fire every time the userdata is accessed, and __newindex every time a value is set. The metatable cannot be obtained. The functions and methods on it can’t even be enumerated. It is essentially a black box to any code looking at it.

But that brings be back to my question, what do they actually store? Metatables aside.

[bonkybincer]

Not sure if this answers your question, but there’s a guide here that explains Userdatas in full, with applications and all.

[au_tk]

Thank you, it didn’t answer my question but rereading the thread made me realize that userdatas could be used to make metatables dependant from tables. If that makes any sense at all. I didn’t learn anything about the actual functionality or what userdatas store though.