From: "David A. Black" <dblack@...>
Date: 2005-02-13T06:22:20+09:00
Subject: Re: const_defined? and inheritance

Hi --

On Sun, 13 Feb 2005, Kevin Howe wrote:

> It seems that const_defined? doesnt search it's superclass:
>
>  class A
>    FOO = 'BAR'
>  end
>
>  class B < A; end
>
>  puts A.const_get(:FOO) # => 'BAR'
>  puts A.const_defined?(:FOO) # => true
>  puts B.const_get(:FOO) # => 'BAR'
>  puts B.const_defined?(:FOO) # => false
>
> I had expected B.const_defined?(:FOO) to be true. Seems strange that
> const_get does the lookup while const_defined? doesn't. Is there a reason
> for this behaviour?
>
> The following takes care of it:
>
>  class A
>    def self.const_defined?(symbol) super ||
> superclass.const_defined?(symbol) end
>  end
>
> But would like to know why this is.

I think they're just two different operations.  The constants a module
can see ("get") is a superset of the constants it's defined.


David

-- 
David A. Black
dblack@wobblini.net