Rails - Oct 2006 - callbacks for to-one associations?

To-many associations have those nice before/after_add/remove  
callbacks. What''s the best way to hook in custom code for to-one  
associations? I want to update a date field every time a certain  
belongs_to association gets changed.

Thanks,
Christian

I wrote:
> To-many associations have those nice before/after_add/remove  
> callbacks. What''s the best way to hook in custom code for to-one  
> associations? I want to update a date field every time a certain  
> belongs_to association gets changed.

The following seems to do the trick. Is there a more elegant  
solution, though?

class Foo < ActiveRecord::Base
   belongs_to :bar

   alias_method :_bar=, :bar
   def bar=(new_bar)
     update_date
     self._bar = new_bar
   end


Thanks,
Christian