Swift：如何在自定义segue之后保留嵌入式导航控制器？

I am trying to set up a custom segue from a view controller that is embedded in a navigation controller. When I use a show segue, everything is fine, the navigation bar remains as expected. However, when I try to use a custom segue class, the navigation bar disappears. After checking, the navigation controller is absent from the post-custom segue view controller. So it seems the problem comes from using a custom segue: how can I stay within the navigation controller with a custom segue? Here is my custom segue code, which purpose is to make the segue have a slide effect from top to bottom:I am trying to set up a custom segue from a vie