noclass.lua

-- class implementation
local function class(t)
  t.__index = t
  return t
end
local function extend(dst,src)
  for k,v in pairs(src) do
    if type(k) == "string" and k:sub(1,1) ~= "_" then
      dst[k] = dst[k] or v
    end
  end
  dst.__index = dst
  return dst
end

-- example class Foo
local Foo = class{
  attr1 = 1,
  attr2 = 2,
}

function Foo:getattr1()
  return self.attr1
end

function Foo:getattr2()
  return self.attr1
end

-- example class Bar which inherits from Foo
local Bar = extend({
  attr3 = 3,
  attr1 = 4,
}, Foo)

function Bar:getattr3()
  return self.attr3
end


-- usage

inst = setmetatable({attr3=1337}, Bar)
print(inst:getattr3(3))