Add dismiss button to Bottom Sheet - ios

Question

In Apple's documentation on Sheet Views, they demonstrate how to instantiate a view controller that displays a Bottom Sheet with a "close" button on the right-hand side. Consider the photo below:
I am having a hard time replicating this. When I present the Sheet View in a NavigationController, and explicitly add a close button, I can see the close button but the sheet becomes a .large() detent. Their photo suggests they are achieving this with a .medium() detent. Documentation for UISheetPresentationController shows no other alternative. Any idea what I am doing wrong?
My SheetController:
override func viewDidLoad() {
....
navigationItem.rightBarButtonItem = UIBarButtonItem.init(barButtonSystemItem: .done, target: self, action: #selector(closeSheet))
....
}
In a different controller, a button click initiates the presentation of the sheetController:
#objc func showTheSheet() {
let updateController = MySheetController()
if let sheet = updateController.sheetPresentationController {
sheet.detents = [.medium()]
sheet.largestUndimmedDetentIdentifier = nil
sheet.prefersGrabberVisible = true
sheet.prefersScrollingExpandsWhenScrolledToEdge = true
sheet.prefersEdgeAttachedInCompactHeight = true
sheet.widthFollowsPreferredContentSizeWhenEdgeAttached = true
}
let navController = UINavigationController(rootViewController: updateController)
self.present(navController, animated: true, completion: nil)
}

Answer 1

Ah, the answer is to wrap the nav controller into the sheet. Silly mistake, but might help someone.
#objc func updateAction() {
let updateController = MySheetController()
let navController = UINavigationController(rootViewController: updateController)
if let sheet = navController.sheetPresentationController {
sheet.detents = [.medium()]
sheet.largestUndimmedDetentIdentifier = nil
sheet.prefersGrabberVisible = true
sheet.prefersScrollingExpandsWhenScrolledToEdge = true
sheet.prefersEdgeAttachedInCompactHeight = true
sheet.widthFollowsPreferredContentSizeWhenEdgeAttached = true
}
self.present(navController, animated: true, completion: nil)
}