title: Hiding a toolbar element when UITableView scrolls (similar to Facebook's app?)
body: <p>How I can achieve this effect?</p>
  
  <p><a href="https://i.stack.imgur.com/zQyuL.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/zQyuL.png" alt="full top view"></a>
   <a href="https://i.stack.imgur.com/1p85b.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1p85b.png" alt="half top view"></a>
   
  <a href="https://i.stack.imgur.com/CXAyR.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/CXAyR.png" alt="top view almost hidden"></a>
  </p>