Cannot find value I'm sure is there

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#1

My first shot at OOP in Roblox is starting off right. On line 25 of the Enemy object (the only line inside of Enemy:MoveTo()), there’s an exception:

22:29:10.795 - ServerStorage.Enemy:25: attempt to index field 'EnemyModel' (a nil value)

Weird part is, the method that calls Enemy:MoveTo() uses EnemyModel, so if it really didn’t exist, then why would Enemy:Move() be working?

Enemy Object

local Enemy = {}
Enemy.__index = Enemy

function Enemy:Move()
	--Get all the player in line of sight
	--Find closest player
	--Charge player
	
	local closest = {nil, nil} -- closest[1] = player, closest[2] = distance
	
	for _,player in pairs(game.Players:GetChildren()) do
		--Add check to see if the zombie is within line of sight of the player
		if player.Character then
			local dist = (player.Character.PrimaryPart.Position - self.EnemyModel.PrimaryPart.Position).magnitude
			if closest[2] == nil or dist < closest[2] then closest = {player, dist} end
		end
	end
	
	if closest[1] == nil then return end
	
	Enemy:MoveTo(closest[1].Character.PrimaryPart.Position)
end

function Enemy:MoveTo(pos)
	self.EnemyModel:MoveTo(pos)
end

function Enemy.new(enemyModel)
	local enemy = { --enemy fields
		EnemyModel = enemyModel
	}
	setmetatable(enemy, Enemy) --enemy methods
	
	enemyModel.Name = "" --get rid of the nametag
	
	return enemy
end

return Enemy

Zombie Object

local Enemy = require(game.ServerStorage.Enemy)

local Zombie = {}
Zombie.__index = Zombie
setmetatable(Zombie, Enemy)

function Zombie.new(enemyModel)
	local zombie = Enemy.new(enemyModel)
	setmetatable(zombie, Zombie)
	
	--Zombie animation, make the arms go up
	local animation = Instance.new("Animation")
	animation.AnimationId = "http://roblox.com/Asset?ID=04842071021"
	enemyModel.Humanoid:LoadAnimation(animation):Play()
	
	return zombie
end

return Zombie

Zombie script

local zombie = require(game.ServerStorage.Zombie).new(script.Parent)

while true do
	zombie:Move()
	
	wait()
end
1 Like
#2

This is a very simple problem which many people tend to make.

You should use the WaitForChild function, if that doesn’t work then let me know.

#3

Generally, if you’re sure there is a model, you use Parent:FindFirstChild(ModelName), which will either return the model or return nil. WaitForChild can and will yield if the script doesn’t find anything.

#4

That wouldn’t make sense because the zombie script, the script making an instance of Zombie, is inside of zombie model and wouldn’t change anything. I still changed

local zombie = require(game.ServerStorage.Zombie).new(script.Parent)

to

local zombie = require(game.ServerStorage.Zombie).new(script.Parent.Parent:WaitForChild(script.Parent.Name))

to no effect.

#5

This has been a test and you all fail. As per usual I figured it out by myself at random.

The reasoning is because I’m calling Enemy:MoveTo() as if it were a static method (to those who don’t know OOP lingo, that is a function of an object that can be run without the object being instanced. See all of the table functions). Simply change the line calling Enemy:MoveTo() to self:MoveTo() and the problem is solved.