From: Robert Klemme <bob.news@...>
Date: 2005-04-29T23:59:29+09:00
Subject: Re: determining when inside 'class << self'


"Ara.T.Howard" <Ara.T.Howard@noaa.gov> schrieb im Newsbeitrag
news:Pine.LNX.4.62.0504282141220.19121@harp.ngdc.noaa.gov...
>
> 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?

Yes, like this:

class Object
   def inside_metaclass?() false end
end

class Class
   def inside_metaclass?
     begin
       self.allocate
       false
     rescue TypeError => e
       /virtual class/i =~ e.to_s and true
     end
   end
end

irb(main):058:0> class <<Object.new; p inside_metaclass? end
true
=> nil
irb(main):059:0> p inside_metaclass?
false
=> nil
irb(main):060:0> class String; p inside_metaclass? end
false
=> nil

Cheers

    robert