Issue with setting background and UINavigationbar attributes swift - ios

Question

in my table view controller it works fine and I can configure the view like so:
func configureView() {
self.tableView.backgroundView = UIImageView(image: UIImage(named: "background.jpg"))
//set custom height for tableview row
tableView.rowHeight = 64
//change the font and size of nav bar text
if let navBarFont = UIFont(name: "HelveticaNeue-Thin", size: 20.0) {
let navBarAttributesDictionary: [String: AnyObject]? = [NSForegroundColorAttributeName: UIColor.blackColor(), NSFontAttributeName: navBarFont]
navigationController?.navigationBar.titleTextAttributes = navBarAttributesDictionary
}
}
When I am trying to configure the view in another view controller (with the same navigation controller) it doesn't work and won't change the background or nav bar font, i use this configureview:
func configureView() {
self.view.backgroundColor = UIColor(patternImage: UIImage(named: "background.jpg")!)
//change the font and size of nav bar text
if let navBarFont = UIFont(name: "HelveticaNeue-Thin", size: 20.0) {
print("fired")
let navBarAttributesDictionary: [String: AnyObject]? = [NSForegroundColorAttributeName: UIColor.blackColor(), NSFontAttributeName: navBarFont]
UINavigationBar.appearance().tintColor = UIColor.redColor()
navigationController?.navigationBar.titleTextAttributes = navBarAttributesDictionary
}
}
Does anyone have any suggestions on how to debug this or what could be going on? My first view controller is a table view, second a normal view. Thanks
Edit: my segue is of type Show, and my prepare for segue is as follows:
if segue.identifier == "showAlertInfoSegue" {
if let viewController = segue.destinationViewController as? AlertViewController {
viewController.tableAlert = nil
//if the sender is the selected table view row - load in the data from the data struct
if sender?.tag != 1 {
viewController.tableAlert = alertDetail
}
viewController.onDataAvailable = {[weak self]
(data) in
if let weakSelf = self {
weakSelf.doSomethingWithData(data)
}
}
viewController.hidesBottomBarWhenPushed = true
}
}
I also see a peculiar grey shadow appearing on the top nav bar when transitioning, then it dissapears