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