title: How to make iOS callback functions?
body: <p>I can't figure out how to make a function, that will give information to the parent object, that has done something, so I need your help.
  Example what I want to make:</p>
  
  <ol>
  <li><code>ViewController</code> class instantiate class <code>BottomView</code> and adds it as it's subview.</li>
  <li>Make a call on instance of <code>BottomView</code> class to start animate something.</li>
  <li>After the animation ends, I want to give a sign that the animation has ended to the <code>ViewController</code> class, that it could release/remove an instance <code>BottomView</code> from itself.</li>
  </ol>
  
  <p>I need something like a callback. 
  Could you help please?</p>