tutorials/tut021_detouring.md


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# Tut 0x021
## Detouring

Detouring is a method commonly used in lua, even outside of gmod development. The idea is to redirect a function through your function first, then call the function you're redirecting at the end (or maybe the beginning, or anywhere really). Let's see an example:

garrysmod/lua/autorun/detourprint.lua

	local oldprint = print
	function print(...)
		local args = {...}
		args[#args + 1] = "if you know what I mean..."
		oldprint(unpack(args))
	end

The above script __replaces__ the print function, with a new function, which eventually calls the original print function, with modified arguments. The above can be done with modules in Artery as well. For example, `log.lua`'s .error() function currently only prints a message in red, it dosn't actually show what failed or why. Let's modify it to show a stack trace.

garrysmod/addons/artery\_rougelite/trace\_errors.lua

	local log = nrequire("log.lua")
	local colors = nrequire("config/colortheme.lua") --Holds colors

	local oldlog = log.error
	function log.error(...)
		oldlog(unpack({...}))
		MsgC(colors.console.red,debug.traceback())
	end


For more information on colortheme.lua see @{colortheme.lua}, for more on debug.traceback() see [the gmod wiki](http://wiki.garrysmod.com/page/debug/traceback).

Next tutorial: @{tut030_inventories.md}