新浪微博开发－创建文件结构和初始化根视图控制器

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        // Override point for customization after application launch.
        window = UIWindow(frame: UIScreen.mainScreen().bounds)
        window?.backgroundColor = UIColor.whiteColor()
        window?.makeKeyAndVisible()
        
        //设置根视图控制器
        window?.rootViewController = MainViewController()
        return true
    }