From: Brian Marick <marick@...>
Date: 2001-10-26T02:15:54+09:00
Subject: [ruby-talk:23318] class Foo does not call Class.new?

It seems that this:
	class Foo
	end
does not invoke Class.new in Ruby 1.6.3. Is that right? Does it in 1.7? 
Should it?

I am assuming that this:
     class Bar
     end
should be just syntactic sugar for
     Bar = Class.new unless Module.constants.include? "Bar"

Here's why I think it isn't. I'm using code like the following to 
demonstrate metaclass hackery for the _Little Ruby_ book. It counts the 
number of instances of any class. (Please note that I'm trying to use as 
little syntax as possible, so the code is not idiomatic.)

class Class

   alias_method("old_new", "new")

   def instances
     if @instances == nil
       @instances = 0
     end
     @instances
   end

   def instances=(val)
     @instances = val
   end

   def count_new_instance
     self.instances += 1
     if superclass
       superclass.count_new_instance
     end
   end

   def new(*args)
     count_new_instance
     old_new(*args)
   end
end

That doesn't work for Class.new (or any class that redefines new). I 
thought it would be cute to make it work, because it lets me round out the 
discussion of what inherits from what. So I did this:

class Class
   @old_class_new = method("new")

   def Class.new(*args)
     count_new_instance
     @old_class_new.call(*args)
   end
end

After this:

Class.instances      #=> 0
Class.new
Class.instances      #=> 1
class Bar
end
Class.instances      #=> 1

--
Brian Marick, marick@testing.com
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