From: Marcelo Alvim <malvim@...>
Date: 2007-04-17T06:34:35+09:00
Subject: "restoring" classes after changing stuff

Hi,

Well, I'm new to Ruby (I've been working and playing with it for the
last 6 months only), and
I know there's probably another way in which this could work, but
somehow I feel like the
code below should work. Let's see what you guys think about it.

The idea is making a copy of a class object, changing it and then
restoring it back to what it was after playing with the new stuff I
added. It should go somewhat like this:

OldArray = Array.dup
# => OldArray

class Array
    def my_method; "My Method"; end
end
# => nil

[].my_method
# => "My Method"

x = Array.new
# => []

x.my_method
# => "My Method"

### Switch back
Array = OldArray.dup
(irb):9: warning: already initialized constant Array
# => Array

x.my_method
# => "My Method"

(Ok, now why did that work? Maybe "x" is still using the modified Array class?)

[].my_method
# => "My Method"

(Same thing here, it seems)

[1, 2, 3].my_method
# => "My Method"

(Hmmmm, let's try something different)

x = Array.new
# => []

x.my_method
NoMethodError: undefined method `my_method' for []:Array
        from (irb):14
        from :0

(Ok, so new instances only? Is this weird at all, or is this the way
it's supposed to work?)

I'm asking these questions out of real lack of knowledge, and I REALLY
don't suppose
something should change in order to make this work. I'm just trying to
understand how
Ruby does all this stuff.

Thank you in advance,
Marcelo Alvim.