基于Swift的应用程序是否可以在OS X 10.9/iOS 7和更低版本上运行？

用于测试的Simple Swift应用程序：

func application(application: UIApplication,didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool {
    self.window = UIWindow(frame: UIScreen.mainScreen().bounds)

    var controller = UIViewController()
    var view = UIView(frame: CGRectMake(0,320,568))
    view.BACkgroundColor = UIColor.redColor()
    controller.view = view

    var label = UILabel(frame: CGRectMake(0,200,21))
    label.center = CGPointMake(160,284)
    label.textAlignment = NSTextAlignment.Center
    label.text = "I'am a test label"
    controller.view.addSubview(label)

    self.window!.rootViewController = controller
    self.window!.makeKeyAndVisible()
    return true
}