From: Patrick Doyle <wpdster@...>
Date: 2008-10-04T04:36:14+09:00
Subject: class << self

Sorry if this is a FAQ, but I was just looking at some Ruby code and
came across the following construct:

class << self
  def blahblahblah
  ...
  end
end

I wondered what that did, went looking, and came across this email
thread from 2002:
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/57244, in
reading that, I came across this (slightly modified) code:

class A
  B = 12
  def self.a
    puts "class method A::a : #{B}"
  end

  def A.b
    puts "class method A::b : #{B}"
  end

  class << self
    B = 24
    def c
      puts "class method A::c : #{B}"
    end
  end

end
A.a
A.b
A.c
puts "A::B : #{A::B}"

Could somebody enlighten me as to what is going on here?  I didn't
completely follow all of the ins & outs of the thread, nor why

def self.a

is better/different than

def A.a

is better different than

class << self
  def a

Can anybody comment or point me in the direction of some enlightenment?

--wpd