SWIFT 通过字符串创建相关的类

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
        // Override point for customization after application launch.
        self.window!.backgroundColor = UIColor.whiteColor()

        self.window?.rootViewController = RootViewController()

        self.window!.makeKeyAndVisible()
        return true
    }

}

import UIKit

class RootViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        let name = "MainViewController"
        //动态获取命名空间
        let namespace = NSBundle.mainBundle().infoDictionary!["CFBundleExecutable"] as! String
        print(namespace)
        //注意工程中必须有相关的类，否则程序会崩
        let cls:AnyObject = NSClassFromString(namespace + "." + name)!
        print(cls)
        // 告诉编译器它的真实类型
        let viewControllerClass = cls as! UIViewController.Type
        let viewController = viewControllerClass.init()
        print(viewController)
    }
}

import UIKit

class MainViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}