Attempt to call a nil value?

Help and Feedback Scripting Support
#1

im trying to learn oop, but when i call newcar:Boost(), it errors this:

  14:01:15.547  ServerScriptService.Script:23: attempt to call a nil value  -  Server - Script:23
  14:01:15.548  Stack Begin  -  Studio
  14:01:15.548  Script 'ServerScriptService.Script', Line 23  -  Studio - Script:23
  14:01:15.548  Stack End  -  Studio

here is the full script:


car = {}
car._index = car

function car.new(pos,model,driver,worldpos,speed)
	local newcar = {}
	setmetatable(newcar,car)
	
	newcar.Position = pos
	newcar.Model = model
	newcar.Driver = driver
	newcar.WorldPosition = worldpos
	newcar.Speed = speed
	
	return newcar
end

function car:Boost()
	self.Speed = self.Speed + 5
end

local newcar = car.new(3,game.ReplicatedStorage.Car,"userni3",Vector3.new(10,0,10),5)
newcar:Boost()
print(newcar)
1 Like
#2

Make sure to require the module script.

#3

i dont have any module script tho

#4

Also make sure to put a car model in replicated storage and use wait for child to make sure it exist if on client.

#5

why is the function called car:Boost and not just Boost

#6

that’s unrelated to the question on the original post

#7

because im trying to learn oop

#8

object oriented programming?–

#9

yes, thats what im trying to learn

#10

Nah, it’s erroring because it’s trying to access the car variable in replicated storage but it doesn’t exist hence a nil error.

Just my bet on it.

#11

it does exist in replicatedstorage

#12

Oh whoops found the issue, it’s a typo with the meta table.

There needs to be 2 underscores

car.__index = car

Then it gets the fancy highlighting.

And it does the metatable redirection from

{--newcar table, doesn't have Boost function without the help of meta table
                    ["Driver"] = "userni3",
                    ["Model"] = Car,
                    ["Position"] = 3,
                    ["Speed"] = 10,
                    ["WorldPosition"] = 10, 0, 10
                 }  -  

--the meta table tells it to index from the car table
 {--car table printed out boost function is accessed here
                    ["Boost"] = "function",
                    ["__index"] = "*** cycle table reference detected ***",
                    ["new"] = "function"
                 }  -  Server - Script:24
1 Like
#13

yeah you’re right -------------

#14

roblox studio autocorrect put 1 underscore instead of two, im dumb

1 Like
#15

if that was the case then, “attempt to call a nil value” wouldn’t have been shown at all

if you look at the code in :Boost() it doesn’t even mess with self.Model, it messes with self.Speed

#16

Yep sorry, that’s a mistake. I was guessing at all the possible nil error possibilities and mixed up attempt to index nil vs attempt to call a nil value (really common problem on #help-and-feedback:scripting-support ).