Attempt to perform arithmetic (sub) on number and nil

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1

so im making a tower defense game, i have everything working, but when i upgrade, i get the error

attempt to perform arithmetic (sub) on number and nil

and it comes from:

 player.stats.Cash.Value -= towercosts.Data[tower.Parent.Name][level]

the towercosts is a module that contains what the towers level cost and how much it costs to place it, the level is the towers current level
and the tower is the tower model

2

towercosts.Data[tower.Parent.Name][level] is nil. Before subtracting the cash try printing towercosts.Data to see if tower.Parent.Name is in fact a key in the table. You can then also check if level is within that table.

3

it just prints

{...}

thats all that prints

5

then how else am i supposed to use modules to store data?

6

Try to separate the table so you find out what index is nil.

print(towercosts.Data)
print(towercosts.Data[tower.Parent.Name])
print(towercosts.Data[tower.Parent.Name][level])

If any one of those are nil, then you can look inside the last [brackets] to see what is missing.
Also, you can open {…} to see what values are inside.

7

the last one was nil, is that why?

8

Next, try this:

print(towercosts.Data[tower.Parent.Name], level)

Open the table that gets printed and see if you can find the 2nd print level anywhere in the table. If not, then your level variable is incorrect.

9

it prints 1 which is the level the tower is getting upgraded to

10

What does the table look like when it is opened? It could be possible that your level variable is a string. consider using tonumber(level) or tostring(level)

11

it looks like this:

                    ["1"] = 50,
                    ["2"] = 100,
                    ["Cost"] = 250
12

I’m guessing level is a number then. You have to do towercosts.Data[tower.Parent.Name][tostring(level)]. Types matter!

1 Like
13

ive never heard of tostring, but ill try!

ok so it works, thanks for telling me