Attempt to perform arithmetic (add) on nil and number

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#1

Hello,
I tried to make a system that adds a item to a table depending on the items type. I get an error saying attempt to perform arithmetic (add) on nil and number Im not sure how to fix this. When i print out the table it is a nil number.

local Inventory = {
	T1= {};
	T2= {};
	T3= {};
	T4= {};
}

Inventory.T1[plr.Name] = {}
Inventory.T2[plr.Name] = {}
Inventory.T3[plr.Name] = {}
Inventory.T4[plr.Name] = {}

local T1 = Inventory.T1[plr.Name]
local T2 = Inventory.T2[plr.name]
local T3 = Inventory.T3[plr.Name]
local T4 = Inventory.T4[plr.Name]

if item ~= T1[item] or item ~= T2[item] or item ~= T3[item] or item ~= T4[item]  then
	Inventory[itemType][plr.Name][item] += 1
elseif item == T1[item] or item == T2[item] or item == T3[item] or item == T4[item] then
	Inventory[itemType][plr.Name][item] += 1
end
1 Like
#2

It’s erroring as there’s no number when you actually try to add one. It’s like doing nil + 1 which obviously errors. You should add a check, and if the item count is nil then set it to 0 and then add 1.

#3

I did this but I don’t get the error but I still get a nill value. How can i fix this?

#4

You set it to 0 like I said right?

#5 

if item ~= T1[item] or item ~= T2[item] or item ~= T3[item] or item ~= T4[item]  then
	if Inventory[itemType][plr.Name][item] == nil then
	   Inventory[itemType][plr.Name][item] = 0
	end
	Inventory[itemType][plr.Name][item] += 1
elseif item == T1[item] or item == T2[item] or item == T3[item] or item == T4[item] then
	Inventory[itemType][plr.Name][item] += 1
end
#6

I just noticed something:
Inventory[itemType][plr.Name][item] += 1
What is “itemType”? I don’t see it defined anywhere.

#7

itemType is a variable from a module
local itemType = ItemModule[item.Name]["Type"]

module:

local module = {
	["Sword"] = {
		Name = "Sword";
		Type = T1;
		Model = Models.Sword;
	};
}

return module
#8

Oh, well then maybe the error is because you’re trying to find that specific item type inside of the player’s inventory, but since it’s nil then it will error.

local Inventory = {
	T1= {};
	T2= {};
	T3= {};
	T4= {};
}

You didn’t define any itemType here, so when you do this Inventory[itemType][plr.Name][item] it doesn’t find an actual “itemType” and it doesn’t work. Maybe I’m wrong but I don’t know your full script so I’m unsure on what is erroring here cause there are no mistakes I’m noticing.

#9

T1 to T4 are the itemtypes, i just have them in a module for each item.

#10

Oh yes sorry lol. If you try printing out the value, I guess it prints nil?

#11

yes, I just found out that if I change Inventory[itemType][plr.Name][item] += 1 to Inventory[itemType][plr.Name][item] = Inventory[itemType][plr.Name][item] + 1 it goes to 1 but doesn’t go higher.

#12

Add a print, see if it actually prints after the value is set to 1:

if Inventory[itemType][plr.Name][item] == nil then
   Inventory[itemType][plr.Name][item] = 0
   print("Reset to 0")
end
#13

image
yes, this gets printed

#14

Does it print everytime? Or just the first time?

#15

Every time for the same item.
image

#16

Oh, that means something is resetting the item count back to nil, since everytime it prints it means the item count is nil.

#17

This whole code if statement is in a function and the parameters is just the item name which is item

#18

How can i fix this? because as far as i know there is nothing that resets the code.

#19

I’m really confused too, as there aren’t any errors. Can I see your script? I’ll try replicating the issue on a baseplate and then try to fix it from there.
(You can DM it if you prefer not to show it to everyone)

#20

I DM’d you a file containing the issue.