First I defined the AppendScript function

local object = {}

local mt = {
        AppendScript = function(self, handler, method)
            local func = self:GetScript(handler)
            self:SetScript(handler, function(...)
                func(...)
            method()
            end)
        end
        }

setmetatable(object, { __index = setmetatable(mt, getmetatable(object)) })

This way I can write

local method = function()
--do stuffs
end
object:AppendScript(handler, method)

for append method to the handler script (`self:GetScript(handler)`) that, for example, I defined previously.

`object` is a client UI form such as frame or button (stored as a table), and `handler` an event ("OnLoad", "OnShow" and so)

I would like to make sure that the function is not appended indefinitely: in a nutshell that the function is not appended every time the event fires.

It was recommended to make the Function Constructor in Metamethod __newindex and decide in AppendScript if it has to be recreated/destroyed, but I'm still a bit inexperienced with metatables.

Can you help me?