title: How to adjust super view 's height base on subview's size in XIB?
body: <p>In xcode 6 ,i create a xib for a custom view (named: ViewA,got a RED background color) ,and ViewA's xib got a file size 600*600, in ViewA ,I put a subview labelB (got a GREEN background color )in it ,and  labelB's numberOfLines = 0 ,so labelB'height is variable , I want the ViewA 's height changed based on labelB's height (e.g ViewA.bottom = labelB.bottom + 10), and I have already pin the labelB's top,bottom,trailing,leading to ViewA, but it still doesn't !work ,the ViewA's height is always 600 ,no matter what label's height is . How can i achieve this goal in auto layout? thanks</p>
  
  <p><img src="https://i.stack.imgur.com/iNmRI.jpg" alt="enter image description here"></p>