Hi, i’ve seen some people use .self especially in modules and i’m just wondering what it is and why it is used?
~~
for example Party system help
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self is basically a thing you can use in OOP to reference the subject, this is useful to access its properties. e.g.
local Car = {}
Car.__index = Car
function Car.new(model, color) -- Making a new car object
local NewCar = setmetatable({}, Car)
NewCar.Model = model
NewCar.Color = color
return NewCar
end
function Car:Properties()
return {self.model, self.color} -- Self is referencing an object we made
end
-- Separate script
local CarModule = require(carmodule)
local MyCar = Car.new("Firebrand", "Red")
print(MyCar:Properties()) -- Prints {"Firebrand, "Red"}
I hope this helped.
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Oh thanks for the example,
When you put lua print(MyCar:Properties()), does the Car:Properties() function know to return the model and colour of MyCar because you called the Properties function with the variable “MyCar” lua MyCar:Properties() instead of “Car” Car:Properties()
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Here’s another random and simple example to demonstrate:
local object = {
PropertyA = 120,
AddToPropertyA = function(self, val: number)
self.PropertyA += val
return self.PropertyA
end,
}
print(object:AddToPropertyA(15)) -- > 135
print(object.AddToPropertyA(object, 15)) -- > 135
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Here you go, there’s a bit more info regarding the “self” parameter here.
and also here.
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The examples here were too overcomplicated so I will give you my explanation.
You use self if you’re calling an object method and want to refer to that object.
These two are equivalent
object:function() == object.function(object)
Example:
local car = {__name = "car name"}
function car:test()
-- automatically references `self` to the `car` object without a need to define it explicitly
print(self.__name)
end
function car.test2(self)
print(self.__name)
end
car:test()
car.test(car)
car.test2(car)
car:test2()
Output:
car name
car name
car name
car name
8 Likes
Thank you, let’s say if I want to refer to each different players’ cars? so e.g. Player1’s car, then Player2’s car how can I get that specific player’s car object?
In this case you would need to create a table and store each players car object in that table.
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A more in-depth explanation of self.
When writing a function in a table, you can write it like this:
local module = {}
function module.new()
--blah blah blah
end
return module
This is the same thing as writing it like this:
local module = {
new = function()
--blah blah blah
end
}
return module
When using a colon : in functions, such as in the case of function module:example(), the colon is often described as “syntax sugar” (although it’d be more accurate to call it “syntactic sugar”, I digress). What this means is that it is not really needed and only exist for the purpose of looking good and simplifying the code.
The : in the declaration is basically passing the table itself as the first parameter in the function. For example
function module:example()
--other code
end
is the same thing as:
function module.example(module)
--other code
end
The module parameter in the second example is the module itself. That is why the self keyword is aptly named self. You may still be wondering how these two example are the same. In that case, if I were to call each of them, then I’d have to do it in two separate ways, like so:
module:example() --first example
module.example(module) --second example
Hopefully, I explained it in a way that was understandable. As a parting gift, here’s a working example of a script that utilizes each method:
local module = {}
function module:example1()
print("Self1: ",self)
end
function module.example2(self)
print("Self2: ",self)
end
module:example1()
module.example2(module)
It will print the table and each function within it in the console.
2 Likes
Thank you very much, I’d like to say I appreciate it i’ve been seeing you helping me a lot on the questions I asked, thank you truly for that 
I’m just wondering on how I should go about creating a party system and if I should use OOP / .self with it?
Self Explanation: What is the self keyword in Lua? - Roblox Studio - YouTube
OOP Intro: https://www.youtube.com/playlist?list=PLXSd5YZgxaXSjGBMAn5FqdtZIG-3Gsp4z
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Given the example party system you used, OOP would be the best method for creating the parties. Whether or not you use the self keyword depends on whether you actually need it. Take for example, a math module with a function that returns whether or not a number is even:
local module = {}
function module.isEven(x : number)
return math.abs(x)%2 == 0
end
return module
In this example, there is no reason it needs the self keyword so it isn’t used. However, in a party object, you will most likely have a Members property that has a list of all the players in the party. If theoretically we had a function that returns a random member in the party, it will need access to the members in it. So, the function might be written like this:
local Party = {}
function Party:IsMember(player) : (boolean, number?)
local index = table.find(self.Members, player)
return (index~=nil), index
end
function Party:AddMember(player : Player) : ()
table.insert(self.Members, player)
end
function Party:RemoveMember(player : Player) : ()
local isMember : boolean, index : number? = self:IsMember(player)
if isMember and index then
table.remove(self.Members, index)
end
end
function Party:GetRandomMember() : Player
return self.Members[math.random(#self.Members)] :: Player
end
return { -- returns a table with the constructor functions
new = function(players : {Player})
local party = setmetatable({}, Party)
party.Members = table.move(players, 1, #players, 1, {}) :: {Player}
return party
end
}
Because this function needs access to all the current members in the party, we use the self keyword. I also added several other function that you might see in a party system.
However, the ones that I are supposed to be private to the object are indexed with a underscore (_) before the name. This is because private and public variables are a concept in OOP, even though they aren’t possible in Lua through easy means (you have to use a proxy and weak references). It’s more for organization than anything else.
Although Roblox is going to release a feature that allows the developer to specify which methods can be seen publicly (outside the module) using the typechecker.
If you do not understand OOP yet, you can take a look at the following resources:
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Thanks, how would I clear a car that was created? If i wanted to remove it later
In that case you could either clear all the values in the car object and then remove the reference you have to it, or just remove the reference you have to it.