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.
}
}