Okay, a metatable is a table in a table, in simple terms. You can create one in two ways:

Code:

setmetatable({}, {})

or

Code:

Table = {["Tab"] = {}}

Those both make metatables. You cam also use the function newproxy() to create a Userdata with a metatable, but that is almost never needed. Though, it would look like this:

Code:

local USERDATA_VAR = newproxy(true)
--false makes no metatable, just an empty userdata
--Now edit it like any other metatable.

Now, time to edit the metatable. These metatables have functions called metamethods. These functions are the things run when you access a metatable. These are the most common metamethods:

Code:

__index = nil
__newindex = nil
--When you access a metatable ('unlocked'), it looks for this thing called an __index. It will run this function attached, this also holds the objects of the metatable. If this is nil, or there is a __newindex object, and this isn't the first time the metatable is accessed, it will run the __newindex method. When that is nil, it returns nil and runs nothing.

__call = nil
--This is run when the metatable is called. It is much less common, but still used a lot. A fun example is when you use it with getmetatable("").__call

__eq = nil
--The == operation

__lt = nil
--The < operation

__metatable = nil
--Can lock the metatable. If this isn't nil, it is run when the metatable is accessed or called.

__mode = nil
--String: Mode. It will return any weakpoints in the metatable values. Not used commonly.

These are majorly used (or most used) metameathods that I CAN THINK OF! I may be missing some, these are off the top of my head. Also, mind my spelling, I typed this quickly at like 4:00 this morning before I left for the day.

Anyways, using a metatable:
One major use is OOP, which stands for Object-oriented programming. This means that you program using mainly objects you already have. Java is a major OOP language for example. Another example is to add protection to your programs. You can remove harmful code using a metatable. A former person named Meelo (Meeloq on Twitter), also found metatables useful for a Big-number calculator (long story). Though, the point is that metatables are useful at the correct times. If you are advanced enough to create a functional metatable. You should be able to run it.

tl;dr: Metatables are useful at the right times. If you can make an error-free syntax-correct one, you can run it also.

I think it would be better if you were clearer on what everything did

I don't see what's so hard about this i use it all the time its easy to under stand I don't think its really expert work.

naknak wrote:

I think it would be better if you were clearer on what everything did

Expert tutorials don't really need to be too clear. They're made for the experts...

flump, it may not be an expert tutorial, but it isn't advanced either. It is between the two, and I just used the same concept medical staffs use, I bumped it up instead of knocking it down =P

this makes sense... but what is userdata?

A userdata is the type Lua uses for data structures in the underlying C program. There aren't native Lua functions for handling those types, they must be handled via Metatables. All Roblox objects and events are userdata Lua type.

Uhhhhhhh... Can you re-clarify?

What everything in roblox is. You are indirectly using them all the time if you script.

:P I understand wiki better than this.

Time to steal from wiki :P

Btw, the wiki is why we made this site. They never update. We on the other hand update everyday.

Quote :

A userdata is the type Lua uses for data structures in the underlying C program. There aren't native Lua functions for handling those types, they must be handled via Metatables. All Roblox objects and events are userdata Lua type.

what does this mean?

It just means everything in roblox is a userdata.

which is? oh come on get to the point. what is userdata?

Its the name of a type or class. It isn't really anything, I guess you can call it a set memory.

but wiki had more info than this. lol, i'm working on my own wiki!

Cool

i kinda get these things, but this tutorial doesn't explain stuff completely. somethings missing. and im going to find out what.

lack of detail