Appending function properly

[Benalish]

First I defined the `AppendScript` function

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 that, for example, I defined previously.

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?

[Fizzlemizz]

It seems a little over complicated. A version of a Mixin for scripts might be easier to get along with for using on a variety of the same widget type.

-- Generic script application function
local function AddScripts(frame, scripts)
    for k, v in pairs(scripts) do
        frame:SetScript(k, v)
    end
end
 
-- Scripts for Buttons
local ButtonScripts = {}
function ButtonScripts.OnClick(self, button, down)
    -- ...
end
function ButtonScripts.OnEnter(self)
    -- ...
end
function ButtonScripts.OnLeave(self)
    -- ...
end
 
-- Create Button, Apply Scripts
local f = CreateFrame("Button", "xxx", UIParent)
AddScripts(f, ButtonScripts)
 
-- Scripts for sliders
local SliderScripts = {}
function SliderScripts.OnValueChanged(self, value)
    -- ...
end
 
-- Create Slider, Apply Scripts
local s = CreateFrame("Slider", "zzz", UIParent)
AddScripts(s, SliderScripts)

Just a thought

[Fizzlemizz]

If you wanted to do it like that (needed to append multiple scripts and not use HookScript) an example would look something like:

local mt = {
    AppendScript = function(self, handler, method)
        local func = self:GetScript(handler)
        self:SetScript(handler, function(...)
            func(...)
            method()
        end)
    end,
}
 
local frame = CreateFrame("BUTTON", "MyParty1", UIParent, "BackdropTemplate")
 
setmetatable(frame, { __index = setmetatable(mt, getmetatable(frame)) })
 
frame:SetSize(200, 40)
frame:SetBackdrop({ bgFile = "Interface\\BUTTONS\\WHITE8X8", tile = true, tileSize = 8 })
frame:SetBackdropColor(0, 0, 0)
frame:SetPoint("CENTER", UIParent, "CENTER", 0, 0)
 
local count = 0
frame:SetScript("OnEnter", function(self) -- Initial SetScript is required so others can be added.
    count = count + 1
    print(count, "First Enter")
end)
 
local function FirstAdded(self) 
    print(count, "First Added On Enter!!!")
end
frame:AppendScript("OnEnter", FirstAdded)
 
local function SecondAdded(self) 
    print(count, "Second Added On Enter!!!")
end
frame:AppendScript("OnEnter", SecondAdded)

[Fizzlemizz]

I kept getting the feeling I was misunderstanding what you are trying to do. Maybe you're looking for a way to run something only the first time a script is used hence the Constructor analogy

This example is a combination of the previous one with the concept of a "constructor" (run once). If you tried to use __newindex you would only get errors trying to do anything with the frame. (I hope this covers it because I'm out of ideas as to what you're looking for )

local mt = {
    AppendScript = function(self, handler, method)
        local func = self:GetScript(handler)
        self:SetScript(handler, function(self, ...)
            if func then -- SetScript() if used
                func(self, ...)
            end
            method(self, ...) -- then appended script
        end)
    end,
 
    ConstructScript = function(self, handler, method)
        local func = self:GetScript(handler)
        self:SetScript(handler, function(self, ...)
            if method then -- Constuctor method runs first
                method(self, ...)
                method = nil
            end
            if func then -- then SetScript() if used.
                func(self, ...)
            end
        end)
    end,
}
 
local frame = CreateFrame("BUTTON", "MyHookedFrame", UIParent, "BackdropTemplate")
 
setmetatable(frame, { __index = setmetatable(mt, getmetatable(frame)) })
 
frame:SetSize(200, 40)
frame:SetBackdrop({ bgFile = "Interface\\BUTTONS\\WHITE8X8", tile = true, tileSize = 8 })
frame:SetBackdropColor(0, 0, 0)
frame:SetPoint("CENTER", UIParent, "CENTER", 0, 0)
 
local count = 0
frame:SetScript("OnEnter", function(self) -- Set/HookScript required to allow other scripts to be appended
    count = count + 1
    print(count, "|cff00ff00First Frame OnEnter Script|r")
end)
 
local function Construct(self, ...) 
    print(count, self:GetName(), "|cffff0000Only going to show you this once!!!|r", ...)
end
frame:ConstructScript("OnEnter", Construct)
 
local function AppendScriptOne(self, ...)
    print(count, self:GetName(), "|cff0000ffFirst Appended On Enter!!!|r", ...)
end
frame:AppendScript("OnEnter", AppendScriptOne)
 
local function AppendScriptTwo(self, ...) 
    print(count, self:GetName(), "|Cffffff00Second Appended On Enter!!!|r", ...)
end
frame:AppendScript("OnEnter", AppendScriptTwo)
 
local frame2 = CreateFrame("BUTTON", "MyHookedFrame2", UIParent, "BackdropTemplate")
 
setmetatable(frame2, { __index = setmetatable(mt, getmetatable(frame2)) })
 
frame2:SetSize(200, 40)
frame2:SetBackdrop({ bgFile = "Interface\\BUTTONS\\WHITE8X8", tile = true, tileSize = 8 })
frame2:SetBackdropColor(0, 0, 0)
frame2:SetPoint("TOP", frame, "BOTTOM", 0, -10)
 
-- Optional SetScript not used here (unless you want to uncomment it.)
--frame2:SetScript("OnEnter", function(self) -- Set/HookScript required to allow other scripts to be appended
--  count = count + 10
--  print(count, "|cff00ff00Second Frame OnEnter Script|r")
--end)
 
frame2:ConstructScript("OnEnter", Construct)
frame2:AppendScript("OnEnter", AppendScriptOne)
frame2:AppendScript("OnEnter", AppendScriptTwo)

Overly complicated!

[SDPhantom]

In general, I have a variable keep track if I have hooked the script and only do so if I haven't.

For example:

local function OnScript(self)
--  Do Stuff
end
 
local Hooked={};
hooksecurefunc(SomeFrameMixin,"SomeMethod",function(self)
    if not Hooked[self] then
        self:HookScript("ScriptType",OnScript);
        Hooked[self]=true;
    end
end);

PS: I don't see a reason to not use :HookScript() when you're essentially reinventing it anyway.