WoWInterface - Frames and metatables

WoWInterface (https://www.wowinterface.com/forums/index.php)

- Lua/XML Help (https://www.wowinterface.com/forums/forumdisplay.php?f=16)

- - Frames and metatables (https://www.wowinterface.com/forums/showthread.php?t=53928)

Benalish

07-19-16 10:33 AM

Frames and metatables

If I have a frame, and the put a metatable on this all this methods, e.g. SetBackdropColor(), are overwritten. There's a solution to overcame this problem?

Lua Code:

local frm = CreateFrame("Frame")
 
local mt = { __index =
    {
        foo = function() print("bar") end
    }
}
    
setmetatable(frm, mt)
 
frm:SetBackdropColor(0,0.5,1)

Error message: attempt to call method 'SetBackdropColor' (a nil value)

Fizzlemizz

07-19-16 10:58 AM

You haven't actually set a backdrop to colour.

semlar

07-19-16 11:23 AM

You can get the original metatable of the frame and set that as your new metatable's metatable, eg.

Lua Code:

local f = CreateFrame('frame')
local mt = {
    foo = function()
        print('bar')
    end
}
setmetatable(f, { __index = setmetatable(mt, getmetatable(f)) })
f.foo()
print(f.SetBackdropColor)

SDPhantom

07-19-16 12:03 PM

You can also copy functions from the old metatable to the new one. This will impose a longer setup time and use up more memory, but will save CPU usage during runtime. Taint is also a problem if the frame is protected, but it's unclear whether the replacement of the frame's metatable would cause taint by itself anyway.

Lua Code:

local frame=CreateFrame("Frame")
local meta={__index={}};
 
-- Define functions after these lines
for name,func in pairs(getmetatable(frame).__index) do meta.__index[name]=func; end
setmetatable(frame,meta);
 
function meta.__index:foo()
    print("bar");
end

kurapica.igas

07-19-16 08:58 PM

It may cause taint, you don't need to replace the frame's meta, it is better to creating a wrapper of the frame like :

Lua Code:

local metaF = {
    __index = {
        foo = function() print("bar") end
    },
}
 
function BuildFrame(...)
    local f = CreateFrame("Frame", ...)
 
    -- Only create the meta once
    if not metaF.Inited then
        metaF.Inited = true
        for k, v in pairs(getmetatable(f).__index) do
            if not metaF.__index[k] then
                metaF.__index[k] = v
            end
        end
    end
 
    -- Create the wrapper
    local w = setmetatable({}, metaF)
    w[0] = f[0]   -- Copy the userdata, make sure the widget API can works well with the wrapper
    -- w.RealUI = f   -- You may add a ref to the real frame
 
    return w
end
 
-- Now you can use it without taint
local frm = BuildFrame()
frm:SetBackdropColor(0,0.5,1)

All times are GMT -6. The time now is 01:13 PM.