From: Assaph Mehr <assaph@...>
Date: 2005-04-29T15:24:27+09:00
Subject: Re: determining when inside 'class << self'


Ara.T.Howard wrote:
> i like a method like this
>
>    def inside_metaclass?
>      # to be implemented
>    end
>
>    class C
>      class << self
>        p inside_metaclass? #=> true
>      end
>
>      p inside_metaclass? #=> false
>    end
>
>    p inside_metaclass? #=> false
>
>    class << []
>      p inside_metaclass? #=> true
>    end
>
> can this be done?


Would you settle for testing if you're inside an anonymous class?
Anonymous classes have names that look like:
#<Class:...>

So you can define your method as:

def inside_metaclass?
  Integer === (self.to_s =~ /^#<Class:/)
end

Which will evaluate to true for anonymous classes. Since (I believe)
all meta-classes are anonymous that can give you a pretty good guess
(or at least has the same result as your sample).

Out of curiosity I've run:
ObjectSpace.each_object { |o| p [o, o.class] if o.to_s =~ /^#<Class:/ }

Which returned ~30 such objects (anonymous classes, unless I'm
mistaken). So unless you're opening an anonymous class, you should be
OK (and I'm not even sure you can reopen an anonymous class).


HTH,
Assaph