Usage of 'self' in a script

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#1

Before you reply, yes, there’s countless topics on self already but I’m left with unanswered questions, I’ve re-read over the topics and I understand the following statements (i think).

  • ‘self’ is passed as the first parameter when you define a module function using : instead of .
  • self is the object that you called the function on?

Some things I’m not too sure on:

‘self’ is a table, is there times where self is an instance and not a table? Will it always be a table? If so, does this heavily tie in with metatables? Is it just used for convenience rather than needed to pass the object as a parameter?

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#2

Instance are userdata.
There are cases where self is userdata

local userdata = newproxy(true) --> fake C userdata
local meta = getmetatable(userdata)

meta.__index = meta

function meta:test()
  print(type(self))--> userdata
end

self does not tie heavily with metatable (usually only in OOP)

local modularprogramming = {}

function modularprogramming:test()
  print(self, self == modularprogramming) --> some memory address, true
end

The : operator is merely a syntax sugar, It is not a must.

game.Destroy(workspace.Part)

works.

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#3

It should be noted that majority of methods on Roblox Instances should be called with a : otherwise it will throw an error.

Edit: I should clarify, using : would require you to not pass the Instance in the parameter. So if you call a method with ., you must pass the instance as well.

#4

It will only throw an error if you did not pass self or passed irrelevant types.
There are some cases where calling it with . is much more concise and quick, not to mention that it just looks visually more appealing.
For example:

local OK, errorOrData = pcall(Datastore.GetAsync, Datastore, PlayerKey)

As opposed to

local OK, errorOrData = pcall(function()
  return Datastore:GetAsync(PlayerKey)
end)
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