How to create a base view controller

Question

I would like to have a BaseViewController that subclasses UIViewController, overrides one of it's methods, but also require it's subclasses to implement new ones.

My case is a bit more complex, but this simple case represents my problem:

My BaseViewController would override viewWillAppear to set it's title, but the title string would come from it's subclasses. I thought about some options, not sure if/which one of them is best.

1 - Class with error throwing methods (my current solution):

class BaseViewController: UIViewController {
  override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    title = getTitle()
  }

  func getTitle() -> String {
    fatalError("Unimplemented method")
  }
}

2 - Receive the title in constructor:

class BaseViewController: UIViewController {
  var myTitle: String!

  convenience init(title titleSent: String) {
    self.init(nibName: nil, bundle: nil)
    myTitle = sentTitle
  }

  override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    title = myTitle
  }
}

Note that this options gets really bad if there's more parameters to send

I thought that using protocol would be perfect, until I find out that (of course) protocols can't subclass a class.

Didn't anybody do anything like this before? I don't think so, please share your thoughts.

Update

I tried another way, but got stuck in a compiler error, would this ever work?

procotol BaseViewController {
  var myTitle: String { get }
}

extension BaseViewController where Self: UIViewController {
  override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    title = myTitle
  }
}

The compiler says Method does not override any method from its superclass.

Answer 1

I usually create protocol in which I declare what would be nice to have in the controllers. Then I check in the base controller if it's actually implemented and if so, just use the values, like this:

protocol ControllerType {
    var navigationTitle: String { get }
}

extension ControllerType {
    var navigationTitle: String {
        return "Default title"
    }
}

class BaseViewController: UIViewController {

    override func viewDidLoad() {
        if let controller = self as? ControllerType {
            self.title = controller.navigationTitle
        }
    }
}

class ViewController: BaseViewController, ControllerType {

    var navigationTitle: String {
        return "ViewController"
    }

    override func viewDidLoad() {
        super.viewDidLoad()    
    }
}

Downfall is you have to implement the ControllerType protocol and there's no way to enforce it.