From: Josh Cheek <josh.cheek@...>
Date: 2010-12-01T01:07:05+09:00
Subject: Re: Confusion about singleton method definition

--0016e68db81c22deb8049647611f
Content-Type: text/plain; charset=ISO-8859-1

On Tue, Nov 30, 2010 at 9:58 AM, Robert Klemme
<shortcutter@googlemail.com>wrote:

> 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/
>
>
I get that result for 1.9.2



$ rvm r.rb
1.8.7(jruby-1.5.2)
333
666
1.8.7(jruby-1.5.3)
333
666
1.9.2(macruby-0.7)
333
666
1.8.7(rbx-1.1.0-20100923)
333
666
1.8.6(ruby-1.8.6-p399)
333
666
1.8.7(ruby-1.8.7-p249)
333
666
1.8.7(ruby-1.8.7-p302)
333
666
1.9.1(ruby-1.9.1-p378)
333
666
1.9.2(ruby-1.9.2-p0)
333
333


$ 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

puts "#{RUBY_VERSION}(#{ENV['RUBY_VERSION']})"
myobj.inner_const
myobj.outer_const

--0016e68db81c22deb8049647611f--