From: Gary Wright <gwtmp01@...>
Date: 2007-03-29T11:51:54+09:00
Subject: Re: Virtual classes and 'real' classes -- why?


On Mar 28, 2007, at 4:42 PM, MenTaLguY wrote:
> There is one slight difference in method lookup between class  
> objects and other objects, though.  While for most objects, the  
> search order could be obtained via:
>
>  class Object
>    def method_search_order
>      [ self.eigenclass ] + self.class.ancestors
>    end
>  end
>
> ...classes also include their ancestor classes' "eigenclasses" in  
> the search:
>
>  class Class
>    def method_search_order
>      ancestors.select { |m| Class === m }.map { |c| c.eigenclass }  
> + self.class.ancestors
>    end
>  end


I noticed that in 1.9 class eigenclasses are arranged in a superclass  
hierarchy but
this is not reflected in the ancestors array.  Is this intentional?

class Object
   def eigenclass
     (class <<self; self; end)
   end
end

p Array.eigenclass.superclass    # #<Class:Object>
p Array.eigenclass.ancestors     # [Class, Module, Object, Kernel,  
BasicObject]

p Class.eigenclass.ancestors     # [Class, Module, Object, Kernel,  
BasicObject]

klass = Class.eigenclass
while klass
   p klass
   klass = klass.superclass
end

# output from loop

#<Class:Class>
#<Class:Module>
#<Class:Object>
#<Class:BasicObject>
Class
Module
Object
BasicObject
TypeError: uninitialized class

It seems that BasicObject doesn't respond to #superclass.