title: Validating a Rails model post-save?
body: <p>I have a model with a couple of accepts_nested_attributes_for.  There is a requirement that I have at least one of each of the nested attributes when saving and moving on.</p>
  
  <p>However, validation occurs pre-save, so when I'm removing an item and moving on, it let's it through.</p>
  
  <p>How can I validate that when I've saved, I have at least one item of each nested type there?</p>