Understanding OOP and all of it's functions, any help?

What are the functions of OOP and what are they useful for? (asked many times), what could the examples be used for when neccessary rather then being used all the time?

You could use something like this:

local Module = NewModule()

But I still don’t understand. You can use functions and use _index for a new function. (i think)

local metatable = {
	__index = function (object, key)
		local num = mathProblem(key)
		object[key] = num
		return num

I had this before and could use it but not neccassary

local a = {1, __add = function(Table,val)
   return  val -  Table[1]
print(a + 4) ----->>>> 3
1 Like

Lua on __index
The use of the __index metamethod for inheritance is so common that Lua provides a shortcut. Despite the name, the __index metamethod does not need to be a function: It can be a table, instead. When it is a function, Lua calls it with the table and the absent key as its arguments. When it is a table, Lua redoes the access in that table. We could declare __index simply as

 Window.mt.__index = Window.prototype

OOP (Object-Oriented Programming)
Metatables and Metamethods

Here is one example on how they are useful: https://mawesome4ever.com/2019/09/13/metatables-the-tool-you-need/

Basically, rather than having to save each service into a variable you can just index it when you need them.

Alright, so there’s an insightful thread about OOP in roblox. Check it out!
But if you just want the explanation of the metamethod, here’s some information.
Simply, when you do table[index], it fires __index. If you do table[index] = value, it fires __newindex. table1 + table2 would fire __add, etc.