From: Robert Klemme <bob.news@...>
Date: 2004-02-01T20:09:52+09:00
Subject: Re: check whether a class is defined, listing all classes


"David Garamond" <lists@zara.6.isreserved.com> schrieb im Newsbeitrag
news:401CC702.9030908@zara.6.isreserved.com...
> Given a string of fully-qualified class name, how do I easily check
> whether the class is defined or not? I hope it's not as 'hard' as I think:
>
>   def class_defined?(classname)
>     m = Class
>     classname.split("::").each { |c|
>       m.constants.include?(c) or return false
>       m = m.const_get c
>     }
>     return true
>   end
>
>   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"
irb(main):012:0>

> A bonus question, how do I list all the defined classes in their fully
> qualified name? Example output:
>
>   Object
>   String
>   FalseClass
>   Struct
>   Struct::Tms
>   File
>   File::Stat
>   ...
>
> (My own code is very ugly, I'm embarrassed to show it :-)

ObjectSpace.each_object( Class ){|cl| p cl}
ObjectSpace.each_object( Class ){|cl| p cl.name}

Regards

    robert