Updating timestamp when adding model via association

What's the proper way to update a models timestamp when you add an object to one of it's associations?

For example, if I have a model, Business, that has_many :addresses, when I add a new Address, I'd like the updated_at timestamp for the business object to get updated.

Doing:

@business.addresses.create(....)

Does not update the updated_at timestamp for @business. What's the best way to get it to update?

Thank you, Kenny

If you're using Rails 2.1 and have ActiveRecord::Base.partial_updates = true, you can try this:

class Address   belongs_to :business   before_save :update_business   private     def update_business       if self.business && self.business_id_changed?         self.business.updated_at = Time.now       end end