title: Update top space constraint for view after hide search bar view
body: <p>I have custom UIView and UISearchBar that are placed as subviews on view controller view.</p>
  
  <p>In some case I need hide search bar view and then I want to resize my custom view. So let's say that search bar has 44 pt of height. If it's visible at the top then my custom view should start with y = 44. But if I set search bar hidden, then my custom view should have y position equal to 0.</p>
  
  <p>I use storyboard and I set all constraints, right I want to update top space constraint that is connected to top layout guide right now. By the default it equal 44 pt. But when I hide my search bar I want set top space to 0 and increase height of custom view by 44 pt.</p>
  
  <p>I suppose that all subviews of the custom view will be updated automatically.</p>
  
  <p>this is how views places on self.view of view controller:</p>
  
  <pre><code>***************
  **search bar***
  ***************
  **custom view**
  ***************
  </code></pre>
  
  <p>After hide search bar it should look like this and entirely overlay superview:</p>
  
  <pre><code>***************
  **           **
  **custom view**
  **           **
  ***************
  </code></pre>