From: Johann Hibschman <johann@...>
Date: 2001-09-26T08:21:22+09:00
Subject: [ruby-talk:21699] Re: manipulating "immutable" objects such as Fixnum from within callbacks & al...

>>>>> "GC" == Guillaume Cottenceau <gc@mandrakesoft.com> writes:

    GC> Well it's more generic than that. See my answer to Lyle. I
    GC> want to use, say, "callbacks" with many parameters and let the
    GC> "callbacks" manipulate the "values" as they want but still be
    GC> able to access to new values from outside of the "callbacks".

Well, I'd recommend either just using arrays as object holders, i.e.

def doit(lst)
  lst[0] += 1
end
l = [1]
doit(l)  ->2
l[0]     ->2

or simply defining a callback class that manages all of the state you
need, like

class Callback
  def initialize(val) @val = val; end
  attr_accessor :val
  def doit() @val += 1; end
end
k = Callback.new 5
k.doit
k.val

i.e. make the "callback function" a method of the class, unlike your
first example.

Hope that helps,

--Johann