title: What is the minimum IOS version for [UIImageView centerXAnchor]?
body: <p>Can someone tell me what the minimum IOS version is for <code>[UIImageView centerXAnchor]</code> I have been looking around and can't find the information. I keep receiving the following error when testing on IOS 8.1.</p>
  
  <pre><code>-[UIImageView centerXAnchor]: unrecognized selector sent to instance 0x7ab46b10
  </code></pre>