Attempt to get length of a nil value

[TyK214]

You can write your topic however you want, but you need to answer these questions:

1. What do you want to achieve? Keep it simple and clear!
   Fix this error

2. What is the issue? Include screenshots / videos if possible!

12:42:20.125  nil  -  Client - rolling_module:38
  12:42:20.125  ReplicatedStorage.folder_container.modules.rolling_module:39: attempt to get length of a nil value  -  Client - rolling_module:39

3. What solutions have you tried so far? Did you look for solutions on the Creator Hub?

Yes and on youtube videos and googled it a ton, none helped

whole script

local rolling_module = {}

rolling_module.rarities = {
	["Rare"] = 100, -- 100 = 10%
	["Uncommon"] = 264, -- 264 = 26%
	["Common"] = 550 -- 550 = 55%
}

rolling_module.abilitys = {
	["Rare"] = {"Reckless"},
	["Uncommon"] = {"Tremor"},
	["Common"] = {"Prankster"} -- if you want two abilitys for one rarity do: {"Common1", "Common2"}
}

rolling_module.chooseRarity = function()
	local randNum = math.random(1, 1000)
	local counter = 0
	
	for rarity, weight in rolling_module.rarities do
		counter += weight
		if randNum <= counter then
			return rarity
		end
	end
end

rolling_module.chooseAbility = function(rarity)
	local abilitys = rolling_module.abilitys[rarity]
	
	print(abilitys)
	local ability = abilitys[math.random(1, #abilitys)]
	return ability
end

return rolling_module

[7eoeb (beoe7)]

This would mean that in the chooseAbility function, the ‘rarity’ parameter is not either “Rare”, “Uncommon”, or “Common”. Add a print statement about the given rarity to debug.

[TyK214]

They are both nil. Though i have no clue why as its a math.Random

[silver4804]

my bad, i didnt read the code through, i was wrong.

[illucyte (illu)]

rolling_module.chooseAbility = function(rarity)
	local abilitys = rolling_module.abilitys[rarity]
	
	print(abilitys)
	local ability = abilitys[math.random(1, #abilitys)]
	return ability
end

what does print(rarity) output?

[7eoeb (beoe7)]

@TyK214

rarity

I’m pretty sure he meant it printed nil, hinting that the issue isn’t int the module but in the script where the module is being called?!

[TyK214]

	local module = require(game.ReplicatedStorage.folder_container.modules.rolling_module)
	
	task.wait(Delay_Time)
	
	wait(0.5)

	local rarity = module.chooseRarity()
	local ability = module.chooseAbility(rarity)

its inside a local script

[7eoeb (beoe7)]

@TyK214

rolling_module.rarities = {
	["Rare"] = 100, -- 100 = 10%
	["Uncommon"] = 264, -- 264 = 26%
	["Common"] = 550 -- 550 = 55%
}

These don’t add up to 1,000, they should since you’re doing math.random(1, 1000)

[SubtotalAnt8185]

@TyK214

local randNum = math.random(1, 1000)

You should change this to

-- @ top of script
local total = 0
for key, value in rolling_module.rarities do
	total += value
end
...
-- in rolling_module.chooseRarity
local randNum = math.random(1, total)

The percentages won’t matter anymore, but that’s probably fine. You can normalize them later.

[Luacathy]

The issue is that your percentages don’t add up to 100% (or 1000 in your case since you’re using math.random(1, 1000)). Currently, your weights add up to 914 (100 + 264 + 550), which means there’s an 8.6% chance (1000 - 914 = 86) that the random number won’t match any of your rarities, causing the function to return a nil value as it’s not set to anything.

Here are the ways you could fix it:

1. Make sure your weights add up to 1000 (or adjust the random number range)
2. Add a fallback return value in case no rarity is selected (though this shouldn’t happen if weights add up correctly)

[Luacathy]

Also, I’d recommend using Random.new():NextInteger() instead of math.random() since it’s actually closer to true random (from what I heard it uses an external source to generate seeds for random generation).