Custom Back Button in UINavigationController and Swift 2.2 Selector

Question

I have a custom back button in my UINavigationController s throughout my app that looks like this:

I have a global function (in a random Swift file; not in a class) that I reference everywhere I need one:

func customBackButton(controller: UIViewController){
  if !iPad(){
    controller.navigationItem.leftBarButtonItem =
    UIBarButtonItem(image:UIImage(named: "back"), style:.Plain, target:controller, action:"goBack")
  }
}

Then in the viewDidLoad of my controllers, I simply call:

override func viewDidLoad() {
    //...
    customBackButton(self)
}

The action selector calls the goBack function which I have defined in every controller that uses a custom back button:

func goBack(){
    //Because of the splitViewController, we have to reference the main nav controller
    if let navController = splitViewController?.viewControllers[0] as? UINavigationController{
      navController.popViewControllerAnimated(true)
    }
}

If you are shaking your head at this implementation, I am wide open to better ways of doing this. :)

Now on to my question...

How do I use the new Swift 2.2 selector syntax to reference goBack like this?

func customBackButton(controller: UIViewController){
  if !iPad(){
    controller.navigationItem.leftBarButtonItem =
    UIBarButtonItem(image:UIImage(named: "back"), style:.Plain, target:controller, action:#selector(controller.goBack))
  }
}

This throws an error because controller is a UIViewController that doesn't contain the goBack() function, even though the actual instance that gets passed in does.

Any ideas?

Answer 1

I haven't tried yet but It should be work if you add your function in the extension of UIViewController

extension UIViewController {
  func goBack(){
    //Because of the splitViewController, we have to reference the main nav controller
    if let navController = splitViewController?.viewControllers[0] as? UINavigationController{
      navController.popViewControllerAnimated(true)
    }
  }
}

When you add your goBack function you should probably reach your goBack function from anywhere.

func customBackButton(controller: UIViewController){
  if !iPad(){
    controller.navigationItem.leftBarButtonItem =
    UIBarButtonItem(image:UIImage(named: "back"), style:.Plain, target:controller, action:#selector(controller.goBack))
  }
}