//创建story对象
UIStoryboard *story = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
// 根据控制器的表示取出控制器
ViewController *vie = [story instantiateViewControllerWithIdentifier:@"story"];
//navigation的根控制器
UINavigationController *nav = [[UINavigationController alloc]initWithRootViewController:vie];
self.window.rootViewController = nav;