From: dblack@...
Date: 2006-04-11T03:21:30+09:00
Subject: Re: Quick syntax question

Hi --

On Tue, 11 Apr 2006, Mark Volkmann wrote:

> On 4/10/06, Austin Ziegler <halostatue@gmail.com> wrote:
>> On 4/10/06, Gregory Seidman <gsslist+ruby@anthropohedron.net> wrote:
>>> Consider the following three class definitions:
>>>
>>> class Foo
>>>   def self.bar
>>>     @@bar
>>>   end
>>>   def self.bar=(val)
>>>     @@bar = val
>>>   end
>>> end
>>>
>>> class Foo
>>>   class << self
>>>     def bar
>>>       @@bar
>>>     end
>>>     def bar=(val)
>>>       @@bar = val
>>>     end
>>>   end
>>> end
>>>
>>> class Foo
>>>   class << self
>>>     attr_accessor :bar
>>>   end
>>> end
>>>
>>> Am I correct in believing that they are equivalent? If not, how do they
>>> differ?
>>
>> They are not equivalent. The first two are the same,
>
> That's good to know. I can't see any reason to prefer the second over
> the first. It's a lot more noisy.

There's a subtle difference between the two ways of defining a
singleton method, though:

X = 1

class C
end

class << C
   X = 2
end

class << C
   def x
     X
   end
end

def C.x2
   X
end

p C.x          # 2 (the X from C's singleton class)
p C.x2         # 1 (the X from outer scope)


David

-- 
David A. Black (dblack@wobblini.net)
Ruby Power and Light, LLC (http://www.rubypowerandlight.com)

"Ruby for Rails" coming in PDF April 15, and in paper May 1!
http://www.manning.com/black