Getting "table index is nil" but the if statement is checking if table is nil

[umamidayo (dayo)]

I’m receiving “table index is nil” but my script explicitly checks for the index that is nil. The script is just setting the value of that dictionary key to a number value when it doesn’t exist. What is a way to ensure that the table index is indeed nil before setting it to 0?

This script is simply to obtain the quantity of an item in the player’s inventory, which is stored in a dictionary of player inventories, storing item names and quantities.

function Inventory.GetQuantity(Player: Player, Item: string)
	if Craftbag[Player.Name][Item] == nil then
		Craftbag[Player.Name][Item] = 0
	end
	
	return Craftbag[Player.Name][Item]
end

Here is a picture of the code with line numbers, since line numbers are useful for seeing where the problem is:

And finally, this is the error logged in the output:

ServerScriptService.Inventory:11: table index is nil

Any clue on this will be helpful. Thanks.

Edit: One more thing, the player’s inventory index:

Inventory[Player.Name] = {}

Is connected to the PlayerAdded event, and the GetQuantity() function is binded to a Gui button, so it’s not possible for the player to trigger the GetQuantity() event before the inventory is created.

[ProgrammingRottie (Rumble)]

The only possible explanation for this is that Item is nil. Print out Item before the conditional statement and see what it prints.

[umamidayo (dayo)]

I forgot to also mention that I’m unable to replicate this on my own account, but I have a game with an active player base that shows the error in the server logs after a few hours. So in order for me to replicate this, I have to wait a few hours after I add the print statement.

The Item is also explicitly checked if it exists at all. When the player fires the RemotEvent, it sends the said string. The string is type checked and also checked if it is a valid item in the Items dictionary. So in order to GetQuantity(), the Item must be a string or it won’t work.

if Items[Item] == nil then return end

So I’m not trying to deny your idea, considering that the GetQuantity() function is called for every item that is changed or added to the inventory, which is at least 50-100 times per player. Considering there are 200+ players playing everyday, this print statement will print at least that amount, which can be a mess and it can be painstaking to visually find the Item. But we’ll give it a try, see you in a few hours.

[ProgrammingRottie (Rumble)]

I see. I still do think that is the issue though, there is no other explanation. I was able to replicate this issue myself:

local Inventory = {
	["Player"] = {};
}

local function GetQuantity(Player, Item)
	print(Player, Item)
	
	if Inventory["Player"][Item] == nil then
		Inventory["Player"][Item] = 0
	end
end

GetQuantity("Player", nil)

Visual representation:

And it produces the same exact output:

  11:13:01.229  Player nil  -  Server - Script:6
  11:13:01.230  ServerScriptService.Script:9: table index is nil  -  Server - Script:9
  11:13:01.230  Stack Begin  -  Studio
  11:13:01.230  Script 'ServerScriptService.Script', Line 9 - function GetQuantity  -  Studio - Script:9
  11:13:01.230  Script 'ServerScriptService.Script', Line 13  -  Studio - Script:13
  11:13:01.230  Stack End  -  Studio

I can’t think of any other explanation for your issue. I hope you do figure it out though!

[umamidayo (dayo)]

That’s actually crazy, I just tested this and the error appeared. I’m not sure why this happened but I added the check to the GetQuantity and it works now.

[ProgrammingRottie (Rumble)]

It happens because technically

if Inventory["Player"][nil] == nil then

is true. Inventory[“Player”][nil] does not exist and you’re checking if it does not exist. However, a key cannot be nil: which is why it errors when you try to assign a value to it.