title: How do I centre/center multiple objects vertically and horizontally in XCode's interface builder?
body: <p>So I've set up my constraints:</p>
  
  <p><img src="https://i.stack.imgur.com/oxxmI.png" alt="enter image description here"></p>
  
  <p>In each device these objects are displaying as expected. </p>
  
  <p><strong>iPhone:</strong></p>
  
  <p><img src="https://i.stack.imgur.com/kxwDc.png" alt="enter image description here"></p>
  
  <p><strong>iPad:</strong>
  <img src="https://i.stack.imgur.com/TOo6g.png" alt="enter image description here"></p>
  
  <p>But not I'd like to control how high up or low down these objects are from the top or bottom of the screen or just centre them. You can see from my screen shot they're not centred horizontally.</p>
  
  <p><strong>What I've tried:</strong></p>
  
  <p>When I try to centre them I keep getting those annoying yellow warnings. I even tried to add a view and put the objects inside the view and setup the constraints then centre that view. I still got errors.</p>
  
  <p>How do I do this correctly?</p>