OOP Class Library

--[[
    A small convenient library I wrote to make OOP easier. Consider it an extra gift ;)
]]
local RunService = game:GetService("RunService")

local Class = {
    classes = {} -- A dictionary of the names of all classes created with class() to the classes
} -- Abstract Base Class for all classes, equivalent of Roblox's Instance
Class.__index = Class

function Class.get(className) -- A wrapper
    return Class.classes[className]
end

function Class:clientOnly(memberName, member)
    if RunService:IsClient() then
        self[memberName] = member
    end
    return member
end

function Class:serverOnly(memberName, member)
    if RunService:IsServer() then
        self[memberName] = member
    end
    return member
end

function Class:super(n) -- Takes in how many parents up, returns parent class
    n = n or 1
    local parent = self
    for _ = 1, n do
        parent = parent.__super__
    end
    return parent
end

function Class:GetSuperclasses()
    local supers = {}
    local classIterator = self.__super__
    if classIterator == nil then return end
    repeat
        table.insert(supers, classIterator)
        classIterator = classIterator.__super__
    until classIterator == nil
    return supers
end

function Class:IsA(class) -- Checks if the classes match; could be class name or object
    class = typeof(class) == "table" and class.__classname__ or class
    local classIterator = self.__class__
    repeat
        if classIterator.__classname__ == class then
            return true
        end
        classIterator = classIterator.__super__
    until classIterator == nil
    return false
end

function Class:init(...)
    local className = self.__classname__
    warn(className .. " does not have a " .. className .. ":init() function.")
end

setmetatable(Class, {
    __call = function(_, name, parent) -- Returns a newly created class, takes string name and parent class
        parent = typeof(parent) == 'string' and Class.get(parent) or parent

        local classInst = {}
        classInst.__index = classInst
        classInst.__classname__ = name -- Class metadata
        classInst.__class__ = classInst
        classInst.__super__ = parent
        classInst.__script__ = getfenv(2).script
        Class.classes[name] = classInst
        setmetatable(classInst, parent or Class)

        function classInst.new(...)
            local instance = setmetatable({}, classInst) -- No cyclic table ref in serialization
            classInst['init'](instance, ...)
            return instance
        end
        return classInst
    end
})

return Class