On Sat, Nov 26, 2011 at 7:58 PM, Bernd Eggink
<monoped@sudrala.de> wrote:
On 21.11.2011 15:15, Leo Razoumov wrote:
On Sun, Nov 20, 2011 at 07:27, Stefan Reich
<stefan.reich.maker.of.eye@googlemail.com> wrote:
Hi guys!
I just created a neat little object system for Lua (5.1) that does pretty
much exactly what I want.
You use it like this:
newThing = object(function() -- could add arguments here too
var1 = 1
local var2 = 'test'
function method1()
var1 = var1+1
end
[[snip]]
An elegant idea, indeed! And 'self' reference is avoided.
1. If the function's environment is made identical to the global environment, any global variable X can be accessed as obj.X. This is at least confusing and contradicts the OO paradigma. Example:
--------------------------------------------------------
y = 222
function Class(c)
x = c
end
function ctor(definition)
return function(...)
local env = setmetatable({}, {__index = _G })
setfenv(definition, env)(...)
return env
end
end
obj = ctor(Class)(1)
print(obj.y) --> 222
--------------------------------------------------------
2. In the example above, obj.x can be read and changed from outside. To prevent this, one would normally make the variable local. This leads to even more weirdness:
--------------------------------------------------------
x = 111
function Class(c)
local x = c
function pr() print("obj.x", x) end
end
function ctor(definition)
return function(...)
local env = setmetatable({}, {__index = _G })
setfenv(definition, env)(...)
return env
end
end
obj = ctor(Class)(1)
print(obj.x, x) --> 111 111
obj.pr() --> 1
obj.x=112
print(obj.x, x) --> 112 111
obj.pr() --> 1
--------------------------------------------------------
I admit that I don't quite understand why the last example behaves as it does. I would be glad if somebody could explain what happens here; I'm experienced in Java, but still a beginner in Lua.
Regards,
Bernd
--
http://sudrala.de
