Every time I perform my show(push) segue the articles VC does not have its navigation bar present to display the title or the back button. I have also checked if the navigation controller has a title as that seemed to be the solution to some cases. The class that performs the segue just sends information. Categories is an enumeration.
You have to wrap your articleVC with another NavigationController. Or instead of using segue, you can push it with navigation controller to reuse the NavigationBar.
let yourArticleViewController = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "articleViewControllerIdentifier") as! ArticleViewController
self.navigationController?.pushViewController(yourArticleViewController, animated: true)