From: Robert Dober <robert.dober@...>
Date: 2007-05-11T06:58:48+09:00
Subject: Re: instance_variables doesn't return unassigned variables

On 5/10/07, Jesse Merriman <jesse.d.merriman@gmail.com> wrote:
> On Thursday 10 May 2007 06:00, Bernd wrote:
> > Hi,
> > I wrote a code like this.
> >
> > class ABC
> >   attr_accesor :first, :second
> > end
> >
> > when I wrote the following:
> >
> > x = ABC.new
> > x.first = "test"
> > puts x.instance_variables
> >
> > the output was only
> >
> > @first
>
> You could deduce them by looking for methods that end in an equals:
Hmm that might not be a good idea, a method ending in equals does not
induce the creation of an instance variable with that name.
One could however put attr on steroids by creating a list of
attributes for the class.
Look at this quick and dirty hack do see if this could be helpfull for you

class Module
  alias_method :orig_attreader, :attr_reader
  def attr_reader *symbols
    @__atts__ ||= superclass.attributes.dup
    @__atts__ += symbols
    @__atts__.uniq!
    orig_attreader *symbols
  end

  def attributes
    @__atts__ || []
  end
end

class A
  attr_reader :a
  attr_reader :a, :b
  puts attributes.join(", ")
end

class B < A
  attr_reader :c
  def initialize
    @c = 42
  end
  puts attributes.join(", ")
end

puts B.new.c

<snip>
>

HTH
Robert
-- 
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw