//
//  AppDelegate.swift
//  Countdown
//
//  Created by Julian Grosshauser on 16/10/15.
//  Copyright © 2015 Julian Grosshauser. All rights reserved.
//

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow? = {
        let window = UIWindow(frame: UIScreen.mainScreen().bounds)
        window.backgroundColor = .whiteColor()
        return window
    }()

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        window?.rootViewController = CountdownController()
        window?.makeKeyAndVisible()
        return true
    }
}


//
//  AppDelegate.swift
//  Countdown
//
//  Created by Julian Grosshauser on 16/10/15.
//  Copyright © 2015 Julian Grosshauser. All rights reserved.
//

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow? = {
        let window = UIWindow(frame: UIScreen.mainScreen().bounds)
        window.backgroundColor = .whiteColor()
        return window
    }()

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        return true
    }
}


--- 
+++ 
@@ -18,6 +18,8 @@
     }()
 
     func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
+        window?.rootViewController = CountdownController()
+        window?.makeKeyAndVisible()
         return true
     }
 }
Set `CountdownController` as root view controller
