From: dblack@...
Date: 2006-10-10T10:25:17+09:00
Subject: Re: "def self.method" vs "class << self; def method"

Hi --

On Tue, 10 Oct 2006, joevandyk@gmail.com wrote:

> What's the difference between
>
> class Foo
>  class << self
>    def foo; end
>  end
> end
>
> and
>
> class Foo
>  def self.foo; end
> end

In the general case of class << obj; def x, vs. def obj.x, there's a
difference in the scoping of constants:

   A = 1
   class C
     A = 2
   end

   c = C.new
   class << c
     def x
       puts A    # this is C's A
     end
   end

   def c.y
     puts A      # this is top-level A
   end

   c.x
   c.y

But I don't think this will loom very large in the class-method case.
Any constants you define in the class scope will be visible in both
the methods.  There may be some way to squeeze a difference out of
them by defining methods in Class or something... but they're
basically interchangeable.


David

-- 
                   David A. Black | dblack@wobblini.net
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org