My model knows nothing about either the view or the controller. I believe
that this is a must.
The controller knows about the model and view, which also makes sense.
When something changes in the model, a NSNotification message is sent to a
defaultCenter queue. Now, I have the view listening for the notification.
The view calls some methods in the model.
So the question is that should the view know about the model? Or should only
the controller know about the model. It just seems a little waste to have
the controller listen for the notification and then just ...