title: iOS 8 Swift navigation bar title, buttons not showing in tab based application
body: <p>I am trying to follow <a href="https://developer.apple.com/library/ios/documentation/WindowsViews/Conceptual/ViewControllerCatalog/Chapters/CombiningViewControllers.html" rel="nofollow noreferrer">this tutorial</a>, <a href="https://stackoverflow.com/questions/27591350/how-to-add-navigation-interface-after-create-a-tab-bar-controller-programmatical">this answer</a>, and <a href="https://stackoverflow.com/questions/21448766/adding-navigation-bar-programmatically-ios-7">this answer</a> to create navigation bars for each of my tabs in a tab-based application in iOS 8 / Swift, but no title or buttons on my navigation bar are showing.</p>
  
  <p>Here is what I have so far:</p>
  
  <pre><code>// AppDelegate.swift
  func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -&gt; Bool {            
      let tabBarController = UITabBarController()
  
      let vc1 = ViewController()
      let vc2 = ViewController()
      let vc3 = ViewController()
  
      let nc1 = UINavigationController(rootViewController: vc1)
      let nc2 = UINavigationController(rootViewController: vc2)
      let nc3 = UINavigationController(rootViewController: vc3)
  
      let controllers = [nc1,nc2,nc3]
  
      tabBarController.viewControllers = controllers
  
      nc1.tabBarItem = UITabBarItem(title: "item1", image: nil, tag: 1)
      nc2.tabBarItem = UITabBarItem(title: "item2", image: nil, tag: 1)
      nc3.tabBarItem = UITabBarItem(title: "item3", image: nil, tag: 1)
  
      window = UIWindow(frame: UIScreen.mainScreen().bounds)
      window?.rootViewController = tabBarController
      window?.makeKeyAndVisible()
  
      return true
  }
  
  // ViewController.swift
  class ViewController: UIViewController, UINavigationBarDelegate {
  
      override func viewDidLoad() {
          super.viewDidLoad()
  
          let navigationBar = UINavigationBar(frame: CGRectMake(0, 0, self.view.frame.size.width, 44))
          navigationBar.backgroundColor = UIColor.blueColor()
          navigationBar.delegate = self;
  
          let navigationItem = UINavigationItem()
          navigationItem.title = "Title"
  
          let leftButton =  UIBarButtonItem(title: "Left Button", style:   UIBarButtonItemStyle.Plain, target: self, action: nil)
          let rightButton = UIBarButtonItem(title: "Right Button", style: UIBarButtonItemStyle.Plain, target: self, action: nil)
  
          navigationItem.leftBarButtonItem = leftButton
          navigationItem.rightBarButtonItem = rightButton
  
          navigationBar.items = [navigationItem]
  
      }
  
      func positionForBar(bar: UIBarPositioning) -&gt; UIBarPosition {
          return UIBarPosition.TopAttached
      }
  }
  </code></pre>
  
  <p>But I am just getting a blank navigation bar on top in the simulator.</p>
  
  <p><img src="https://i.stack.imgur.com/j5Tw4.png" alt="iPhone 6 simulator screenshot"></p>