From: Robert Klemme <shortcutter@...>
Date: 2010-12-01T00:58:04+09:00
Subject: Re: Confusion about singleton method definition

On Mon, Nov 29, 2010 at 5:30 PM, David Unric <dunric29a@gmail.com> wrote:
> I'm just learning Ruby from The Well-grounded Rubist book and I cann't
> understand why I cann't get the same results as in author's example.
>
> It's about the difference between defining singleton method directly on
> an object and using class << construct.
> Rephrased example follows:
>
> MYCONST=666
>
> myobj = Object.new
>
> class << myobj
>  MYCONST=333
> end
>
> def myobj.outer_const
>  puts MYCONST
> end
>
> class << myobj
>  def inner_const
>    puts MYCONST
>  end
> end
>
>
> myobj.inner_const call displays 333 (singleton constant value) as
> expected,
> however myobj.outer_const call also displays 333 whereas it should
> display the value of outer (global) MYCONST definition, ie. 666.

Does it?

16:55:39 ~$ allruby r.rb
CYGWIN_NT-5.1 padrklemme2 1.7.7(0.230/5/3) 2010-08-31 09:58 i686 Cygwin
========================================
ruby 1.8.7 (2008-08-11 patchlevel 72) [i386-cygwin]
333
666
========================================
ruby 1.9.1p430 (2010-08-16 revision 28998) [i386-cygwin]
333
666
========================================
jruby 1.4.0 (ruby 1.8.7 patchlevel 174) (2009-11-02 69fbfa3) (Java
HotSpot(TM) Client VM 1.6.0_21) [x86-java]
333
666
16:55:55 ~$ cat r.rb

MYCONST=666

myobj = Object.new

class << myobj
 MYCONST=333
end

def myobj.outer_const
 puts MYCONST
end

class << myobj
 def inner_const
   puts MYCONST
 end
end

myobj.inner_const
myobj.outer_const
16:56:57 ~$

> Did changed language definition recently somehow or is the example
> and/or description in the book simply flawed ?

Can you show _exactly_ the code you executed?

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/