From: Nathan Smith <nsmith5@...>
Date: 2006-08-25T01:21:16+09:00
Subject: Re: Call functions of superclass

On Fri, 25 Aug 2006 dblack@wobblini.net wrote:

> Hi --
>
> On Thu, 24 Aug 2006, Nathan Smith wrote:
>
> > Hello,
> >
> > On Thu, 24 Aug 2006 dblack@wobblini.net wrote:
> >
> >> No; it will point to the superclass of the class of self :-)
> >>
> >>    class C
> >>    end
> >>    class D < C
> >>    end
> >>    D.new.class.superclass   # C
> >
> >
> > I think we are using different terminology. Take a look at this code:
> >
> > class A
> >  def A.hi
> >    puts "A.hi"
> >  end
> >
> >  def hi
> >    puts "hi"
> >  end
> > end
> >
> > class B < A
> >  def hi
> >    self.class.superclass.hi
> >  end
> > end
> >
> > b = B.new
> > b.hi
> >
> >
> > This will output
> >
> > A.hi
>
> Yes, because B.new.class.superclass is A, and A responds to "hi".  The
> method A.hi is defined in A's singleton class (or "metaclass") -- but
> the object to which you are sending the message "hi" is A, not A's
> singleton class.
>
> > In "Programming Ruby", they define the "metaclass" as the object which
> > contains the class-wide objects of the class. IE, the metaclass of A would
> > contain A.hi, and not A#hi (I could be getting the notation of A.hi and
> > A#hi backwards, or completely wrong -- A.hi is the class method, and A#hi
> > is the instance method.)
> >
> > Therefore, in B#hi, self.class.superclass does not refer to the superclass
> > of B -- rather it refers to the metaclass of the super of B. If it pointed
> > to the superclass of B, then calling
> >
> > self.class.superclass.hi
> >
> > would print "hi", instead of "A.hi"
>
> No, because A is the superclass of the class of "self" in your
> example.  A is an object in its own right; it responds to "hi".
>
> I think you're adding an extra level of reference or indirection or
> something.  Look at this:
>
> irb(main):001:0> class C; object_id; end
> => 1615634
> irb(main):002:0> C.new.class.object_id
> => 1615634
> irb(main):003:0> C.new.class.superclass.object_id
> => 1683084
> irb(main):004:0> C.new.class.superclass
> => Object
> irb(main):005:0> Object.object_id
> => 1683084
> irb(main):006:0> class << C; object_id; end
> => 1615554
>
> As you can see, the singleton class of C is not the same object as
> either C or the class of C.
>
> ("Singleton class" is the most general term; the Pickaxe uses
> "metaclass" to mean singleton class of a Class object.  I tend to just
> use "singleton".)

I concede your point -- I was using singleton as the object-specific
class, while it is the opposite of that. Thanks for the clarification.
Maybe now my arguments will make more sense!

Nate