title: Rails Updating Data in one Model from another Model's Controller
body: <p>I have a User model that has billing_id. I have Order model that runs transactions with a payment gateway which returns a billing id I'd like to save into the billing_id column on the User model. I think I am getting the basics of MVC architecture mixed up. </p>
  
  <p>I am under the impression that UsersController and OrdersController update data of their respective tables. Does that mean that if I have something returned from OrdersController such as a billing id, there is no other way of saving that billing id into a billing_id column in User model? Thanks and sorry if this is extremely rudimentary. :)</p>
  
  <p>Also, I thought a possible solution might be to somehow pass in the return value via ApplicationsController into UsersController to save into User table. Is this possible?</p>