Uses Swift to create a UITabBarController and set it as the rootViewController in the AppDelegate.

AppDelegate.swift

    var window: UIWindow?


    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        print("here")
        
 
        self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
        
        let nav1 = UINavigationController()
        let first = ClassNameOne(nibName: "Nib Name One", bundle: nil)
        nav1.viewControllers = [first]
        
        let second = ClassNameTwo(nibName: "Nib Name Two", bundle: nil)
        let nav2 = UINavigationController()
        nav2.viewControllers = [second]
        
        let third = ClassNameThree(nibName: "Nib Name Three", bundle: nil)
        let nav3 = UINavigationController()
        nav3.viewControllers = [third]
        
        let tabs = UITabBarController()
        tabs.viewControllers = [nav1, nav2, nav3]
        
        let firstImage = UIImage(named: "icon.png")
        let secondImage = UIImage(named: "icon.png")
        let thirdImage = UIImage(named: "icon.png")
        
        first.tabBarItem = UITabBarItem(
            title: "Title One",
            image: firstImage,
            tag: 1)
        
        second.tabBarItem = UITabBarItem(
            title: "Title Two",
            image: secondImage,
            tag:2)
        
        third.tabBarItem = UITabBarItem(
            title: "Title Three",
            image: thirdImage,
            tag:3)
        
        self.window!.rootViewController = tabs;
        self.window?.makeKeyAndVisible();
        
        return true
    }