TableTop simulator lua singleton class template

TTS LUA : singleton class template

local MySingleton = {}
MySingleton.__index = MySingleton
setmetatable(MySingleton, {__call = function (cls, ...) return cls.GetInstance(...) end })
local instance

function MySingleton.GetInstance()
    if instance == nil then
        instance = setmetatable({}, MySingleton)
    end
    return instance
end

function MySingleton:SetData(newData)
    self.data = newData
end

function MySingleton:PrintData()
    print(self.data)
end

function MySingleton:DoStuff()
    print("doStuff!!")
end

return MySingleton