title: Using UIStackView with a UITextView with dynamic height
body: <p>I just found out about UIStackView, and I'm trying to see if it can finally make it easier to lay out expanding content.</p>
  
  <p>Specifically, I want to do the following:</p>
  
  <pre><code>|-- UITextView ------------|
  | some dynamic text here,  |  I want the text view's height to change
  | it could be short, or it |  depending on the height of the text
  | could be tall            |  (set later, in code)
  |-- UIView ----------------|
  |xxxxxxxxxxxxxxxxxxxxxxxxxx|  I want this view to expand to fill the 
  |xxxxxxxxxxxxxxxxxxxxxxxxxx|  vertical space.
  |xxxxxxxxxxxxxxxxxxxxxxxxxx|  
  |xxxxxxxxxxxxxxxxxxxxxxxxxx|  It should start right below the
  |xxxxxxxxxxxxxxxxxxxxxxxxxx|  bottom of the UITextView
  |xxxxxxxxxxxxxxxxxxxxxxxxxx|
  |--------------------------|
  </code></pre>
  
  <p>I think I know how to do this with regular constraints. Is it possible to do with UIStackView? I might be understanding the purpose of UIStackView, but I would love to be able to create layouts like this more easily. </p>
  
  <p>When I put both of these into a UIStackView, Interface builder says "Needs constraints for: Y position or height" for both views. </p>