Change the font on the back button of a navigation controller under swift 4

Question

Swift 4, iOS 11.2.5 Xcode 9.2

Trying to change the font of the back button. Tried previous solutions found, but none seem to work under Swift 4, iOS 11.2.5 with my configuration, navigation controller within a tab bar controller.

Got this code, the first and last lines work, but the center three do not.

self.navigationController?.navigationBar.titleTextAttributes = [ NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!]
navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .normal)
navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .highlighted)
navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .focused)
navigationItem.title = "Filter \(titleSelection!) [shake to clear]"

This is in viewDidLoad method. Should this work?

Answer 1

For Swift 4, try this in AppDelegate.

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

        UIBarButtonItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor.red, NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 15)!], for: UIControlState.normal)
        
        UIBarButtonItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor.green, NSAttributedStringKey.font : UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)! ], for: .highlighted)
        UIBarButtonItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor.blue, NSAttributedStringKey.font : UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)! ], for: .focused)
        
        return true
}

In ViewController.

override func viewWillAppear(_ animated: Bool) {
    
    self.title = "List"
    self.navigationController?.navigationBar.titleTextAttributes = [ NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!]

    // THE BELOW THREE LINES NOT WORKING.
 
    //navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .normal)

    //navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .highlighted)

    //navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .focused)

}

Storyboard

Output