From: Lloyd Zusman <ljz@...>
Date: 2008-02-13T22:13:24+09:00
Subject: Re: Test for instance method existence?

Nobuyoshi Nakada <nobu <at> ruby-lang.org> writes:

> 
> Hi,
> 
> At Wed, 13 Feb 2008 19:58:56 +0900,
> Todd Benson wrote in [ruby-talk:290915]:
> > > How can I test if an instance method is defined for a class, without
> > > having to create an instance of that class?
> > >
> > > [ ... ]
> > 
> > I don't know if it's the best way, but there is #instance_methods
> >
> [ ... ]
>
> It's nice to find all matching methods, but inefficient when
> you know the exact name what you want to know.
> 
>   $ ruby -e 'p String.method_defined?(:length)'
>   true

I have a related question.  How do I test whether a certain function is
defined within TOPLEVEL_BINDING?  For example:

  def foobar
    puts "toplevel foobar"
  end

  class X
    def self.foobar
      puts "class X foobar"
    end
    def test_foobar
      # print "exists" if "foobar" is defined within
      # the top level; print "doesn't exist" if "foobar"
      # is not defined within the top level.
    end
  end

  x = X.new
  x.test_foobar

What do I put within the test_foobar method to tell me whether the top-level
function "foobar" is defined? Also, I don't want that method to get confused
by the existence of "self.foobar" within class X.

Thanks in advance.

-- 
 Lloyd Zusman
 ljz@asfast.com
 God bless you.