Question on over laying LUA

I'm working on some updates for the GURPS ruleset and want to do some stuff when an item in the "inventory" window is changed for "equipped/carried/not carried".

I would like to hook the Event on the char_invlist.lua during the onCarriedChanged which seems logical to me.

I attempted to overlay this in my base.xml using:

<script name="CharInvList" file="campaign/scripts/char_invlist.lua" />

after copying the script to the campaign folder in GURPS.

On load of FG however I have problems:

Runtime Notice: Reloading ruleset
Script Error: [string "campaign/scripts/char_invlist.lua"]:25: attempt to call global 'getDatabaseNode' (a nil value)
Script Error: [string "campaign/scripts/char_invlist.lua"]:13: attempt to call global 'registerMenuItem' (a nil value)

Now, I could be doing something completely noob on this but somewhere in my reading I saw a note saying you can't always overlay certain codeblocks?? Thinking maybe that was it...

I then did my changes by over laying the code for "manager_char.lua" using:

<script name="CharManager" file="campaign/scripts/manager_char.lua" />

The only way I could see to hook the "equipped/carried/not carried" in this script is by putting my code in the "updateEncumbrance" code block.

It works!! But I don't like hooking it there as it is inefficient because every time ANY item is changed it goes through ALL the items to recalculate the Encumbrance.

So, my question is, can I over layer char_invlist.lua and/or is there a better way to capture this event so I can do my code?

Thanks in advance, I am quite new to LUA and moding in FG so I know there are holes in my understanding.

PS. Before anyone jumps me on it, I am running my changes through ronnke already, I just don't want to wear him out with my dumb questions and it seems unlikely I'm the first to run into this.)

Happy gaming!

AHA! Thanks to Moon Wizard I finally had the epiphany that had eluded me. I will try to explain but feel free to correct anything I say inaccurately. I've only been playing with lua for less than a month.

I don't need any of the above! I can create a code block and include it in the base.xml and by adding an easy to connect Handler get what I need. Actually, I almost had this in a code block I had tossed aside because I had just missed the correct code by a hair.

So for those like myself who didn't get the memo:

You can create your own lua codeblock and add it to the base.xml file using:

<script name="WhatIWantToDo" file="campaign/scripts/whatever_you_want_to_do.lua" /> <-- use whatever directory is appropriate obviously.

Then in your whatever_you_want_to_do.lua code make sure you have in your onInit() a DB.addHandler(... <-- DB.addHandler is a part of what comes along with FG.

For example:

function onInit()

print("INITIALIZING WHAT I WANT TO DO");
DB.addHandler(DB.getPath("charsheet.*.inventorylist.*.carried") , "onUpdate", onCarriedChanged); <-- this is the event I wanted to hook to but it could be anything.

end

Then you can have your code for the onCarriedChanged:

function onCarriedChanged(nodeCarried)

-- whatever you want to do here

end

One more question though:

I figured I wanted to have a 'removeHandler' in the onClose() block but when I attempted to duplicate the addHandler and change it to removeHandler all I got was an error about it.
example:

in the onInit --> DB.addHandler(DB.getPath("charsheet.*.inventorylist.*.carried") , "onUpdate", onCarriedChanged); <-- this is the event I wanted to hook to but it could be anything.
in the onClose --> DB.removeHandler(DB.getPath("charsheet.*.inventorylist.*.carried") , "onUpdate", onCarriedChanged); <-- this is the event I wanted to hook to but it could be anything.

Here is the error on /reload obviously:

Runtime Notice: Reloading ruleset
Script Error: [string "campaign/scripts/char_item_equip.lua"]:12: attempt to index global 'DB' (a userdata value)

So, I don't have it now and it doesn't say boo but it seems like I missed out on some housekeeping.

edit: seems like after reading some past posts I probably didn't need to try to do this. So I'm going with that until told otherwise. :)

Hope this helps others as much as it has me. Thanks again Moon Wizard.

Oh, and for those wondering what this is all about here's a brief video of what I'm doing:
https://youtu.be/ePQFhu1dugg