From: "Mauricio Fernández" <batsman.geo@...>
Date: 2002-12-02T05:12:06+09:00
Subject: Re: [FAQ] What do some of Ruby's symbols mean?

On Mon, Dec 02, 2002 at 02:54:03AM +0900, Shannon Fang wrote:
> Hi 
> 
> I appreciate the benefit. But some problem not clear:
> 
> 1. what is the symbol %{ mean? I knew there are %w %Q %q etc, but %{ ??
> 2. My inital question about << is class << anObj.  Don't know when it
> became class << self?? Is << only used with self?
> 
> After I understand why class << self, and re-read the pickaxe, I'll be
> able to under stand your code better.
> 

I assume you do already know singleton classes (and methods), so here's
only the explanation of the class << self idiom.

Inside a class definition, 'self' refers the the class object (that of
class Class):
irb(main):001:0> class A
irb(main):002:1> puts self
irb(main):003:1> end
A
nil
irb(main):004:0>

So when we do 'class << self' we're grabbing the current class object's
singleton class to add to it a singleton method which will become a class method:

So 
	class A
		class << self
		def doit
			puts "BLA"
		end
		end
	end

is mostly equivalent to
	class A
		def A.doit
			puts "BLA"
		end	
	end

See one of Guy's (ts) posts on this thread for more info.

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