Lua atempt to call a nil method - lua

Question

I'm having trouble understanding why this code results in an error. Shouldnt the line t.__index = self make sure the table t looks up the init function in Vector?
Vector = {}
Vector.init = function(self,x,y)
self.x = x
self.y = y
end
mt = {}
mt.__call = function(self,...)
local t = {}
t.__index = self
setmetatable(t,self)
t:init(...)
return t
end
setmetatable(Vector,mt)
Vector.__add = function(self,other)
return Vector(self.x+other.x,self.y+other.y)
end
local t = Vector(5,5)
local l = Vector(5,5)
local v = l + t
print(v.x,v.y)
Im also terrible with lua code. I usually use someone else's class library as i cant write my own. Just seems confusing to me.
Ive revised my code as follows.
Vector = {}
Vector.__index = Vector
Vector.mt = {}
Vector.init = function(self,x,y)
self.x = x
self.y = y
end
setmetatable(Vector,Vector.mt)
Vector.mt.__call = function(self,...)
local t = {}
setmetatable(t,self)
t:init(...)
return t
end
Vector.__add = function(self,other)
return Vector(self.x+other.x,self.y+other.y)
end
local t = Vector(5,5)
local l = Vector(5,5)
local v = l + t
print(v.x,v.y)
Works as intended
I came up with this as a general class system
Class = {}
Class.mt = {}
setmetatable(Class,Class.mt)
Class.mt.__call = function(self,name)
local class = {}
class.name = name
class.__index = class
class.mt = {}
class.mt.__call = function(self,...)
local t = {}
setmetatable(t,self)
t.init(t,...)
return t
end
setmetatable(class,class.mt)
return class
end
Vector = Class("Vector")
Vector.init = function(self,x,y)
self.x = x
self.y = y
end
Vector.__add = function(self,other)
return Vector(self.x+other.x,self.y+other.y)
end
I have no idea how to do inheritence
I feel like giving up. Im not good at this
I seemed to have achieved multiple inheritance via mixins.
Just need to declare the super functions before creating the sub classes or else it will not mixin the functions.
Class = {}
Class.mt = {}
setmetatable(Class,Class.mt)
Class.mt.__call = function(self,name,...)
local class = {}
class.name = name
class.parents = {...}
class.__index = class
class.mt = {}
for k,v in pairs(class.parents) do
for i,j in pairs(v) do
if
i ~= "init" and
i ~= "parents" and
i ~= "mt" and
i ~= "__index" and
i ~= "name" then class[i] = j end
end
end
class.mt.__call = function(self,...)
local t = {}
setmetatable(t,self)
t.init(t,...)
return t
end
setmetatable(class,class.mt)
return class
end
Vector = Class("Vector")
Vector.init = function(self,x,y)
self.x = x
self.y = y
end
Vector.__add = function(self,other)
return Vector(self.x+other.x,self.y+other.y)
end
Vector.update = function()
print("update from vector")
end
Vector3 = Class("Vector3",Vector)
Vector3.init = function(self,x,y,z)
print("hello")
Vector.init(self,x,y)
self.z = z
end
Vector3.__add = function(self,other)
local v = Vector.__add(self,other)
return Vector3(v.x,v.y,self.z+other.z)
end
a = Vector3(1,2,3)
a.update()
print(a.z)