From: "Elf M. Sternberg" <elf@...>
Date: 2005-09-29T03:46:43+09:00
Subject: Python to Ruby: Two puzzlements...

I'm afraid that I'm coming from Python, a B&D language where I'm used to
everything be spelled out cleanly, and although I programmed in Perl for
many years that was also many years ago.  Ruby is baffling the heck out
of me.

I've been looking at two examples, and I was wondering if someone could
explain to me what the Hell is going on.  The first is from
http://redhanded.hobix.com/bits/hyperextended.html, and my question is
about the 'extend' keyword there.  Where does that came from?  In what
object is it defined?  It's just hanging there in space.  In the same
breath, what does the 'super' keyword do in the append_features()
method, and why does it need a 'self' in front of it?  I've tried
reading ruby-docs without finding much illumination.

module Mix
   def inst_meth
     puts 'inst_meth'
   end

   module ClassMethods
     def class_meth
       puts 'class_meth'
     end
   end

   extend ClassMethods

   def self.append_features(klass)
     super
     klass.extend(ClassMethods)
   end
 end


Second, I've seen the following constructions:

validates :url :with => %r{^http:.+\.(gif|jpg|png)$}i

        and

check_associations %w(friends downloads links)

I'm guessing that the "%r" and "%w" are the ruby equivalents of perl's
qr{} and qw{} constructs (does this mean there's a %qq() and %qx() as
well?), but I can't find documentation to that effect inside the
references available on-line.  (And before someone says "Buy the
Pickaxe!" I'll just say that I spent my book budget this month on the
Rails book and any other purchases will have to wait until my next
paycheck.)

        Thanks!

                Elf