attempt to index local 'def' (a nil value) - class

Question

I'm working on a game. At a certain point, I would like to create special GameObject. The special GameObject is called Projectile and is the same as GameObject but has a dx and dy as well as some other functions that only a projectile will have. I am trying to make Projectile extend the GameObject class, but I run into issues when I try to create an instance of Projectile. I've tried different ways of declaring Projectile and shuffling declaration order but can't seem to figure out why I'm getting the error mentioned in the title. Thank you!
The following works just fine:
table.insert(self.dungeon.currentRoom.objects, GameObject(
GAME_OBJECT_DEFS['pot'],
self.player.x,
self.player.y
))
But when I change "GameObject" to "Projectile" it does not.
table.insert(self.dungeon.currentRoom.objects, Projectile(
GAME_OBJECT_DEFS['pot'],
self.player.x,
self.player.y
))
The rest is supporting code. I'm using Class code from Matthias Richter
require 'src/Projectile'
require 'src/GameObject'
require 'src/game_objects'
GameObject = Class{}
function GameObject:init(def, x, y)
-- string identifying this object type
self.type = def.type
self.texture = def.texture
self.frame = def.frame or 1
-- whether it acts as an obstacle or not
self.solid = def.solid
self.defaultState = def.defaultState
self.state = self.defaultState
self.states = def.states
-- dimensions
self.x = x
self.y = y
self.width = def.width
self.height = def.height
-- default empty collision callback
self.onCollide = def.onCollide
end
Projectile = Class{__includes = GameObject}
function Projectile:init()
GameObject.init(self, def)
self.dx = 0
self.dy = 0
end
GAME_OBJECT_DEFS = {
['pot'] = {
type = 'pot',
texture = 'tiles',
frame = 14,
width = 16,
height = 16,
solid = true,
defaultState = 'idle',
states = {
['idle'] = {
frame = 14,
}
},
onCollide = function()
end
}
}

Answer 1

function Projectile:init()
GameObject.init(self, def)
self.dx = 0
self.dy = 0
end
def is nil
so in
function GameObject:init(def, x, y)
-- string identifying this object type
self.type = def.type
you index a nil value.
Same will happen for x and y