参考：https://www.jianshu.com/p/df4390b43dd6
func stringToViewController(controllerName:String) -> UIViewController{
let namespace = Bundle.main.infoDictionary!["CFBundleExecutable"] as! String
let cls:AnyClass = NSClassFromString(namespace + "." + controllerName)!
let vcCls = cls as! UIViewController.Type
let vc = vcCls.init()
return vc
}
