From: daz <dooby@...10.karoo.co.uk>
Date: 2003-06-20T12:31:42+09:00
Subject: Re: class X;  class << X        : what is this idiom ?


"you CAN teach an old dog ..." <itsme213@hotmail.com> wrote in message news:a6e48b6b.0306181426.62e8d934@posting.google.com...
> I have seen this idiom quite a few times, and have not figured out
> what it does (looking at the pickaxe book). Could someone help
> enlighten me?
>
> [My guess is that it creates a customized meta-class that X is an
> instance of; am I guessing right?]


That sounds a bit comp.sci :-)

It's usually a prelude to one or more class method definitions.

http://www.rubygarden.org/ruby?ClassMethods


class Roo
  class << Roo         # or class << self
    def class_meth1
    end

    def class_meth2
      p 'class_meth2'
    end
  end

  def Roo.class_meth3  # The usual(?) way
    p 'class_meth3'
  end

  def inst_meth1
    p 'inst_meth1'
  end
end

Roo.class_meth2
Roo.class_meth3

r1 = Roo.new
r1.inst_meth1
r2 = Roo.new
r2.inst_meth1

#-> "class_meth2"
#-> "class_meth3"
#-> "inst_meth1"
#-> "inst_meth1"


daz