local _airtime = {
tick = 0
}

function _airtime.new (o)
      o = o or {}   -- create object if user does not provide one
      o.execCall = function() o:exec() end
      setmetatable(o, self)
      self.__index = self
      return o
end

function _airtime:exec()
    if self.tick == 0 then
        self.tick = 1
        print("airtime exec")
    end
end

local a = _airtime.new()

local function realtime(var) --toggle
    if isEventHandlerAdded("onClientRender", getRootElement(), var.execCall) then
        var.tick = 0
    else
        addEventHandler("onClientRender", getRootElement(), var.execCall)
    end
end