title: Cannot preview IBDesignable custom component on Interface Builder
body: <p>I'm trying to make a custom UI component which can be previewed on Interface Builder.  First I tried to code by myself but I couldn't make it (it works on the built app but cannot be previewed on IB.)</p>
  
  <p>Of course I suspected my code's wrong so I grabbed the project from the tutorial which I made reference to.</p>
  
  <p><a href="https://cheesecakelabs.com/blog/building-custom-ui-controls-xcodes-interface-builder/" rel="nofollow noreferrer">https://cheesecakelabs.com/blog/building-custom-ui-controls-xcodes-interface-builder/</a></p>
  
  <p>But the result is just showing a rectangle, instead of showing two buttons in the custom component.
  I built the project but it didn't take effect to the preview.</p>
  
  <p>The reason I think is one of the below, but basically I have no clue about its further detail. Does anybody have any idea? </p>
  
  <ol>
  <li>There was some changes in InterfaceBuilder since the tutorial of
  above link was written(Sep 2017) </li>
  <li>The tutorial is wrong from the beginning </li>
  <li>I have a wrong configuration in XCode/InterfaceBuilder</li>
  <li>I am misunderstanding the purpose of the above tutorial, and buttons on that custom component cannot be previewed in any ways</li>
  </ol>
  
  <p>Or if anybody has an experience of success/fail in previewing this custom component please let me know as well.</p>
  
  <p>Thanks!</p>