Can someone teach me metatables?

Help and Feedback Scripting Support
#1

my english is not really bad but i just cant learn metatables, i just dont understand them.

Can someone just explain it examples please?
I dont understand the things in roblox wiki / devforum etc

1 Like
Is it worth learning metatables
#2

Please follow the guidelines for posting in the Scripting Support Category - About the Scripting Support category. For metatables, you may reference this - https://developer.roblox.com/en-us/articles/Metatables

2 Likes
#3

As @Scripter_123 mentioned, this probably isn’t the best place to ask this. #discussion would probably be better for this kind of topic.

I remember being confused on what the purpose of metatables is and why they were so confusing to understand. The word “meta” means “referring to itself”. Metatables are just pieces of data that refer to how the table they’re attached to preforms certain operations. For example, you can attach a custom handler when a table is passed into a “tostring” call via the __tostring metamethod. This custom handler can return a customized string based on the data in the table (or anything really). The most practical metamethods are usually:

  • __index
  • __newindex
  • __tostring

Once you understand those, you’ll understand the rest, even though you won’t use them 95% of the time. You usually won’t use metatables unless you’re working with object-oriented programming. I recommend this article to learn more about that.

3 Likes
#4

As @Scripter_123 stated, you are breaking the guidelines. Not only that but this question has been asked many times before. If I were you I’d read the metatables wiki article carefully. There is nothing not understandable or hard.

2 Likes
#5

Metatables are used to extend the functionality of tables.

For instance, using the __index to create a field when its first accessed.

local t = setmetatable({},{
    __index = function(self,key)
        if key == "field" then
            self.field = 1
            return 1
        end
    end
})
print(rawget(t,"field")) --> nil
print(t.field) --> 1
print(rawget(t,"field")) --> 1

Metatables can also be used to allow you to do things like adding tables together (__add), or adding custom equality checks (__eq), and much more.

A list of all metamethods:
http://lua-users.org/wiki/MetatableEvents

2 Likes
#6

Half of those aren’t even supported or rather it’s more difficult to read for those who aren’t as well versed in Lua as others (e.g. not knowing what version we use, which holds roots in 5.1 but extends from other versions as well).

I don’t think linking the Lua Users Wiki is appropriate for this case. The metatable page on the Developer Hub includes metamethods currently Roblox-supported.

https://developer.roblox.com/en-us/articles/Metatables

1 Like