Lua OOP multiple instances of class are being ignored, why? - oop

Question

I have a class called "Edit"
function Edit:new(x,y,w,h,text,fnt)
o = {}
setmetatable(o,EditMt)
self.__index = self
self.x = x or 0
self.y = y or 0
self.width = w or 10
self.height = h or 10
self.text = text or ""
self.active = false
self.font = fnt or font
self.yo = -(self.height - self.font:getHeight()) / 2
return o
end
and that class has a function called draw(made with Löve2d)
function Edit:draw( )
if self.active then
love.graphics.setColor(255,255,255,255)
love.graphics.rectangle("fill",self.x,self.y,self.width,self.height)
love.graphics.setColor(0,0,0,255)
love.graphics.printf(self.text,self.font,self.x,self.y,self.width, "center",0,1,1,0,self.yo)
else
love.graphics.setColor(255,255,255,255)
love.graphics.rectangle("line",self.x,self.y,self.width,self.height)
love.graphics.printf(self.text,self.font,self.x,self.y,self.width, "center",0,1,1,0,self.yo)
end
end
and in my main i create 2 of them
edit1 = Edit:new(10,10,60,50,"1")
edit2 = Edit:new(80,10,60,50,"2")
and draw them in the callback
function love.draw( )
edit1:draw()
edit2:draw()
end
but it only draws edit2? if i switch the places in draw it still only draws edit2 but if i switch their places while creating them in the main it now only draws edit1?

Answer 1

This is the most common beginners mistake when they get into OOP in Lua.
You're assigning all those values to self which is Edit. But if you want to change your instance you need to assign them to o.
Otherwise each call to Edit.new will overwrite the values.
The second problem is that your instance o is a global. You need it to be local! Or you will overwrite your instances each time.
function Edit:new (x,y,w,h,text,fnt)
local o = {}
setmetatable(o, self)
self.__index = self
o.x = x or 0
o.y = y or 0
-- and so forth
return o
end
Read this:
https://www.lua.org/pil/16.html
http://lua-users.org/wiki/ObjectOrientedProgramming

Answer 2

You initiates your object not quite correct.
In new function you initiates your object and self in this function is your metatatable.
The other problem that you creates global object o.
So your new function must be:
function Edit:new(x,y,w,h,text,fnt)
local o = {}
setmetatable(o, self)
self.__index = self
o.x = x or 0
o.y = y or 0
o.width = w or 10
o.height = h or 10
o.text = text or ""
o.active = false
o.font = fnt or font
o.yo = -(o.height - o.font:getHeight()) / 2
return o
end