OOP in lua

local function new( class , ... )
	if ( !class ) then 
		error( "no Class!" )
		return NULL
	end


	if ( class.interface ) then 
		error( "cant instance a interface!" )
		return NULL
	end


	local obj = table.Copy( class )


	if ( obj.ctor ) then obj:ctor( ... ) end--elseif ( obj.super.ctor ) then obj.super:ctor( ... ) 

	return obj
end 


local function class( class , extends )
	if ( !class || type( class ) != "table" ) then 
		error( "no / invalid Class!" )
		return NULL
	end
	if ( extends ) then
		if ( extends.interface ) then 
			for k , v in next, extends do
				if ( !class[k] && k != "interface" ) then error( "interface! " ..  k .. " not implemented" ) end
			end
		else
			local cs = table.Copy( extends )
				  cs.super = extends
			for k ,v in next, class do cs[k] = v end
			class = cs
		end 
	end

	//meta tables
	return class
end 


local function interface( class ) 
	     class.interface = true
  return class
end 
----tests----tests----tests----tests----tests----tests---
-------------------------class---------------------------
local test = class{//class
	me   = 1,
	ctor = function( this )
		print( "cool" )
	end,
	print = function( this )
		print( this.me )
	end
}


local obj = new( test )//object
	  obj:print( )
	  obj.me = 5
	  obj:print( )	  
--------------------------interface----------------------
local person = interface{//interface and its keys
	name = true,
	alter= true,
	test = true,
}


local me = class( { 
	name = "",
	alter = 1,
	test = function( this )
		print( "ich bin " .. this.alter .. " und heiße " .. this.name )
	end,
	ctor = function( this , name , alter ) 
		this.name = name
		this.alter = alter
	end
}, person )//class implements interface




local test = new( me , "K0e" , 18 )
test:test()


local test2 = new( me , "jemand anderes" , 32 )
test2:test()


test:test()
--------------------------extend----------------------
local base_pizza = class{ //class
	name  = "",
	preis = 1,
	ctor = function( this , name , preis ) 		
		this.name = name
		this.preis = preis
	end
}


local magarita = class({ 
	ctor = function( this , name , preis ) 
		--setfenv( 1 , this )--no this 4 super!
		this.super:ctor( name , preis )		
	end,
	print = function( this ) 
		print( this.super.preis ) 
		print( this.super.name  )
	end
} , base_pizza )//class extends base_pizza


local pizza = new( magarita , "Hawaii" , 1.50 )
	  pizza:print()