title: UINavigationBar doesn't appear
body: <p>I can't understand why Navigation Bar doesn't appear.</p>
  
  <p>For example, I tried to add Navigation Bar like this:</p>
  
  <pre><code>1) File -&gt; new project -&gt; single view application -&gt; storyboard -&gt; viewcontroller -&gt; attributes inspector -&gt; Top Bar -&gt; Navigation Bar. 
  </code></pre>
  
  <p>It appear at storyboard, but doesn't appear when app run on simulator</p>
  
  <p>Also I can't understand why it doesn't appear as a subview
  In <code>viewDidLoad</code>:</p>
  
  <pre><code>UINavigationBar *navBar = [[UINavigationBar alloc] init];
  
  [self.view addSubview:navBar]; 
  </code></pre>