From: Robert Klemme <bob.news@...>
Date: 2004-02-01T21:39:50+09:00
Subject: Re: check whether a class is defined, listing all classes


"David Garamond" <lists@zara.6.isreserved.com> schrieb im Newsbeitrag
news:401CEDC9.8000804@zara.6.isreserved.com...
> Robert Klemme wrote:
> >>  p class_defined?("Test::Unit::TestCase") # false
> >>  require 'test/unit/testcase'
> >>  p class_defined?("Test::Unit::TestCase") # true
> >>
> >>Is there an easier way?
> >
> > irb(main):009:0> defined? Test::Unit::TestCase
> > => nil
> > irb(main):010:0> require 'test/unit/testcase'
> > => true
> > irb(main):011:0> defined? Test::Unit::TestCase
> > => "constant"
>
> But what if the class name to be checked is a string?
> ("Test::Unit::TestCase")?

irb(main):005:0> eval "defined? " + "Test::Unit::TestCase"
=> nil
irb(main):006:0> require 'test/unit/testcase'
=> true
irb(main):007:0> eval "defined? " + "Test::Unit::TestCase"
=> "constant"


> Btw, is "defined?" a method (of what class?)?
> A statement?

It's an operator:
http://www.rubycentral.com/book/tut_expressions.html

> >>A bonus question, how do I list all the defined classes in their fully
> >>qualified name? Example output:
> >
> > ObjectSpace.each_object( Class ){|cl| p cl}
> > ObjectSpace.each_object( Class ){|cl| p cl.name}
>
> Ah, Class#name... Thanks, I'm so glad it's straightforward & easy.


:-)

    robert