No storyboard with Swift(Storyboard無しの場合)

An App Delegate class with no storyboard

[AppDelegate.swift](以下のように修正）

import UIKit
@UIApplicationMain
class AppDelegate : UIResponder, UIApplicationDelegate {
 var window : UIWindow?
 func application(application: UIApplication, 
      didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?)
      -> Bool {
           self.window = UIWindow()
           self.window!.rootViewController = UIViewController() // 適用したいViewController
           self.window!.backgroundColor = .white
           self.window!.makeKeyAndVisible()
           return true
   }
}


#Subview and Superview
  func application(application: UIApplication,
            didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?)
            -> Bool {
                self.window = UIWindow()
                self.window!.rootViewController = UIViewController()
                // subviewsの追加ができる
                let mainview = self.window!.rootViewController!.view
                let v = UIView(frame:CGRectMake(100,100,50,50))
                v.backgroundColor = .red // 小さい四角
                mainview.addSubview(v) // main viewに追加
                self.window!.backgroundColor = .white
                self.window!.makeKeyAndVisible()
                return true
}