Swift String转Class

let nameSpage = Bundle.main.infoDictionary!["CFBundleExecutable"]
let childVcClass = NSClassFromString((nameSpage as! String) + "." + clsName)

 if  let appName: String? = NSBundle.mainBundle().objectForInfoDictionaryKey("CFBundleName") as! String? {
        let classStringName = "_TtC\(appName!.characters.count)\(appName!)\(className.characters.count)\(className)"
        let  cls: AnyClass? = NSClassFromString(classStringName)
  }