Dataclass in luau in Roblos Studio

[surreal heart]

Hey all, so I am super new to Roblox Studio and I have a pretty simple question
I want to make sure I understand stuff correctly and wanted to ask, what is the best way make a "Dataclass" like in Roblox Studio?

Say I have an inventory system, how could I implement a simple class to just hold an "InvetoryItem" and its properties? so for example, if I had to do it in python, it would look something like -

from dataclasses import dataclass

@dataclass
class InvetoryItem:
  name: str
  amount: int
  ...

Also, I know that in this case I should probably use ModuleScript, but what's the reasoning behind it?
Thank you all very much in advance!

[idle relic]

im not the best scripter here by i think you can probably use nested dictionaries

inside a module script if you want wide accessibility

[stuck cobalt]

First of all, VERY good post!
There are a few ways to accomplish this.
A good way is to use metatables and lua OOP if you wanna create different objects. Something like this (in a module script)

local InventoryItem = {}
InventoryItem.__index = InventoryItem

function InventoryItem.new(name: string, amount: number)
    local self = setmetatable({}, InventoryItem)
    self.name = name
    self.amount = amount
    return self
end

function InventoryItem:GetDisplayName()
    return string.format("%s (x%d)", self.name, self.amount)
end

return InventoryItem

local InventoryItem = require(moduleScriptPath)

local bottle = InventoryItem.new("Glass Bottle", 1)
print(bottle.name)

And you should also look into some OOP guides!

https://www.lua.org/pil/16.html

[stuck cobalt]

Get your self confidence up king 🙏

[idle relic]

i am working on it

thaks for the kind words

[stuck cobalt]

me too

[surreal heart]

Wow, thank you very much for the detailed answer!

In addition, could I ask why do you have the lines

local InventoryItem = {}
InventoryItem.__index = InventoryItem

at the top? I have seen it in the past through my research but still kind of confused as to what they are actually for.

Also, why a ModuleScript? What are its advatanges in this case?

Either way I will for sure take the time to look more into OOP, thank you!

[wild ice]

its for metatables

[surreal heart]

I see I see

[surreal heart]

Is it possible to add type hinting to metatables?
from my understanding, they are like dynamic data classes, so my IDE (in this case Roblox Studio) won't be able to to auto complete me for example, or give me warnings about wrong types

[stuck cobalt]

https://devforum.roblox.com/t/guide-to-type-checking-with-oop/1997394

[surreal heart]

Awesome, thank you!

[stuck cobalt]

No worries, good luck!

[spice snow]

There are more oop patterns without metatables

[surreal heart]

I'd love to hear alternative ways if you could

[cunning nymph]

** You are now Level 1! **

[stuck cobalt]

That’s why I said ”a few ways to accomplish this”.

[lyric onyx]

yes, you can enable strict type checking mode by writing —!strict at the top of your script.

You can also define variable types as well as casting:

local x: Number = 5 —defining type

local x = calculate() :: Number — casting

Highly recommend you look up the documentation on typechecking, there’s a ton of cool stuff like union types and custom enums you can use, as well as exporting types for use elsewhere

[stuck cobalt]

Roblox does not support custom enums?

[lyric onyx]

you can effectively get the same result with or types

type myEnum = “hello” | “goodbye”

I forgot the documentation name of these, but this is how I use it

[spice snow]

yes

it does

just using like tables

[stuck cobalt]

not in the same way Java does. it’d be better if you could just do the following

enum myEnum {
  enum1,
  enum2
}

and again they don’t have built in custom enum support.

[lyric onyx]

it functionally does the exact same thing

as what I just described

[stuck cobalt]

No. What you described is type restriction, it doesn't create a runtime object or enum, it just tells the type checker what values are allowed for a specific variable, and what is not.

local greeting: myEnum = "hello"  -- valid
local greeting: myEnum = "hi"     -- invalid

The closest you can get in any conventient way is just using tables, but those aren't enums

[lyric onyx]

it does the same damn thing bro

[stuck cobalt]

If you read my message you’d be able to understand that it clearly does not