From: Robert Klemme <shortcutter@...>
Date: 2008-02-13T22:29:49+09:00
Subject: Re: Test for instance method existence?

2008/2/13, Lloyd Zusman <ljz@asfast.com>:
> 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.

eval("self", TOPLEVEL_BINDING).method(:foobar) rescue false

>     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.

YWC

robert

-- 
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