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What does this "attempt to concatenate field '?' (a nil value)" error message mean?

Asked by
StoneFox_Alfa 5
5 years ago

So I'm trying to get my gun system to create an impact sound and play a random sound from a table of sound IDs. It works.. ish. Sometimes the sound will play, but when they don't it throws this error. I'm detecting impacts with the client and firing it over using a RemoteEvent to the server to execute the hit code. Got no idea what's going on here.

--// Client Code

hitEvent:FireServer(p,cross,angle,normal,"Part",h)

--// Server Code

local Meta = Instance.new("Sound")
Meta.Name = "Crack" 

if h.Material == Enum.Material.Grass or h.Material == Enum.Material.Ice or h.Material == Enum.Material.Fabric or h.Material == Enum.Material.Pebble then
    Meta = Crack:FindFirstChild('Crack') or Instance.new('Sound',Crack)
    Meta.Name = 'Crack'
    Meta.SoundId = "rbxassetid://" .. DirtSounds[math.random(0,#DirtSounds)]
end

if h.Material == Enum.Material.Sand then
    Meta = Crack:FindFirstChild('Crack') or Instance.new('Sound',Crack)
    Meta.Name = 'Crack'
    Meta.SoundId = "rbxassetid://" .. SandSounds[math.random(0,#SandSounds)]
end

if h.Material == Enum.Material.Glass or h.Material == Enum.Material.Neon then
    Meta = Crack:FindFirstChild('Crack') or Instance.new('Sound',Crack)
    Meta.Name = 'Crack'
    Meta.SoundId = "rbxassetid://" .. GlassSounds[math.random(0,#GlassSounds)]
end

if h.Material == Enum.Material.Wood or h.Material == Enum.Material.WoodPlanks then
    Meta = Crack:FindFirstChild('Crack') or Instance.new('Sound',Crack)
    Meta.Name = 'Crack'
    Meta.SoundId = "rbxassetid://" .. WoodSounds[math.random(0,#WoodSounds)]
end

if h.Material == Enum.Material.Metal or h.Material == Enum.Material.CorrodedMetal or h.Material == Enum.Material.DiamondPlate then
    Meta = Crack:FindFirstChild('Crack') or Instance.new('Sound',Crack)
    Meta.Name = 'Crack'
    Meta.SoundId = "rbxassetid://" .. MetalSounds[math.random(0,#MetalSounds)]
end

if h.Material == Enum.Material.Water then
    Meta = Crack:FindFirstChild('Crack') or Instance.new('Sound',Crack)
    Meta.Name = 'Crack'
    Meta.SoundId = "rbxassetid://" .. WaterSounds[math.random(0,#WaterSounds)]
end

if h.Material == Enum.Material.Concrete or h.Material == Enum.Material.Plastic or h.Material == Enum.Material.SmoothPlastic or h.Material == Enum.Material.Slate or h.Material == Enum.Material.Foil or h.Material == Enum.Material.Brick or h.Material == Enum.Material.Granite or h.Material == Enum.Material.Marble or h.Material == Enum.Material.Cobblestone then
    Meta = Crack:FindFirstChild('Crack') or Instance.new('Sound',Crack)
    Meta.Name = 'Crack'
    Meta.SoundId = "rbxassetid://" ..                       ConcreteSounds[math.random(0,#ConcreteSounds)]
end 

    Meta.Volume = math.random(0.8,1)
    Meta.EmitterSize = 10
    Meta.MaxDistance = 30
    Meta.Pitch = math.random(0,0.6)
    Meta.Parent = Crack
    Meta:play()

--// Error Message

17:10:12.344 - Stack Begin
17:10:12.344 - Script 'Players.StoneFox_Alfa.Backpack.Editing Model.Program_Server', Line 442
17:10:12.345 - Stack End
17:10:12.443 - Players.StoneFox_Alfa.Backpack.Editing Model.Program_Server:442: attempt to concatenate field '?' (a nil value)
0
Where do you define 'WoodSounds' or 'SandSounds', etc.? Pojoto 329 — 5y
0
In a few tables for each material set. StoneFox_Alfa 5 — 5y
0
just as "1234567" but real ids StoneFox_Alfa 5 — 5y
0
The parent argument to Instance.new is deprecated. Do not use it. User#19524 175 — 5y
View all comments (3 more)
0
It says this 442, which is this line of code is always the problem: Meta.SoundId = "rbxassetid://" .. ConcreteSounds[math.random(0,#ConcreteSounds)] StoneFox_Alfa 5 — 5y
0
^ Lua table indexes are from 1 and up, you would want it to be ConcreteSounds[math.random(1,#ConcreteSounds)]. The error just means that you're concatenating (..'ing) something that's nil, and ConcreteSounds[0] is going to be nil. User#22604 1 — 5y
0
I thought they were from 0 oof thanks StoneFox_Alfa 5 — 5y

1 answer

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Answered by
lazycoolboy500 597 Moderation Voter
5 years ago

To "concatenate" means to "link together" which means that you are trying to make it as one. Sorta like adding 1+2 but in this case, you cannot connect something that doesn't exist with a value.

What I recommend doing is adding an "if" statement that checks whether "h" is not "nil."

if h ~= nil then
    --Your code here
end

If you have any questions or issues, please contact me. ;)

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