ios – Including a Button to the Navigation Bar in Swift

I am attempting so as to add the identical button to the navigation bar of every of my screens. I created the next class:

import UIKit

class UIHelper {

static func addEnvelopeIcon(to viewController: UIViewController) {
    let envelopeImage = UIImage(named: "feedback")
    let envelopeButton = UIBarButtonItem(picture: envelopeImage, fashion: .plain, goal: viewController, motion: #selector(viewController.envelopeButtonTapped))
    viewController.navigationItem.rightBarButtonItem = envelopeButton
    
}

static func showCommentPopup(from viewController: UIViewController, sourceViewControllerName: String) {
    let alert = UIAlertController(title: "Go away a Remark", message: "From: (sourceViewControllerName)", preferredStyle: .alert)
    alert.addTextField { textField in
        textField.placeholder = "Enter your remark right here..."
    }

    let submitAction = UIAlertAction(title: "Submit", fashion: .default) { _ in
        let remark = alert.textFields?.first?.textual content ?? ""
        print("Remark from (sourceViewControllerName): (remark)")
    }

    alert.addAction(submitAction)
    alert.addAction(UIAlertAction(title: "Cancel", fashion: .cancel, handler: nil))

    viewController.current(alert, animated: true, completion: nil)
}
}

I name it like this:

override func viewDidLoad() {
    tremendous.viewDidLoad()
    UIHelper.addEnvelopeIcon(to: self)
}

The button does not seem. No errors are thrown and I’ve verified that the feedback.png picture is in Property.