Lua in method 'addSellableItem' attempt to index a nil value (local 'it')

[siolyolekk]

Hello i working for TFS 1.4.2 when i added NPC then have this bug in console
why can't I refer to if it:getId() ~= 0 then

 

[Wusse]

Try:

if it and it:getId() ~= 0 then

 

[Gesior.pl]

why can't I refer to if it:getId() ~= 0 then

ItemType(id or name) returns ItemType object, if parameter is number or string, otherwise it returns nil.
It means that in 13 line of Timur.lua you try to add some item using addSellableItem, but value passed as ID is not a number/string.
Your value is probably table or nil:

• table in case your parameters are in wrong order and you passed 'item names list' as id/name of item
• nil in case you use variable as item ID and this variable is not defined

Valid code from TFS 1.4:

shopModule:addSellableItem({'empty potion flask', 'empty flask'}, 7636, 5, 'empty small potion flask')

Code that passes table as item ID/name, because I added 1 parameter at start, so list of item names is 2nd parameter now and script uses it as item ID/name:

shopModule:addSellableItem('invalid parameter moves all next parameters to +1 position', {'empty potion flask', 'empty flask'}, 7636, 5, 'empty small potion flask')

Code that passes nil as item ID/name, because I replaced item ID 7636 with variable notItemIdVariable, but in code above I declared this ID as variable itemId, so notItemIdVariable does not exist = is set to nil:

local itemId = 7636
shopModule:addSellableItem({'empty potion flask', 'empty flask'}, notItemIdVariable, 5, 'empty small potion flask')

Your code with if it == nil then should detect these kinds of problems, but real problem is in Timur.lua.
Your code if it == nil then would also generate error in console, because it's bugged, but error would be different. Problem with your code is that print at end tries to concat itemid into string print("[Warning (...)" .. itemid) and you cannot concat string with nil or table and it will throw error. Safe code is to pass itemid as 2nd parameter to print, so it would be `print("[Warning (...)", itemid). Then itemid will be processed by print as separate variable and it will be printed with TAB separator from warning message.

For future:
Often we can't help you without viewing your code. You posted some screenshot with some lines and with line numeration disabled. IDK which line is 916 on that screenshot. Next time post files that are reported in error, in this case: data/npc/lib/npcsystem/modules.lua and data/npc/scripts/Timur.lua.