Rails - Jul 2006 - Clearing dependent collections

I have a user model that owns messages :

class User < ActiveRecord::Base
   has_many :messages , :dependent => :nullify
end


I''m using nullify so that when the user is deleted, the messages  
continue to exist - they''re just marked as being ownerless.

However, calling user.messages.clear actually deletes all his  
messages, which I was a little surprised at.  I would have expected  
it to just set the user_id on all his messages to null, given I''m not  
using :dependent => :destroy/:delete.

Is this intentional?  Is there an equivalent call which will just  
disassociate the messages?  (Obviously I could use something like  
user.messages.each {|m| m.update_attribute(user_id, nil)} - is there  
anything actually built in?)

Jon