NavBarButtonStub.swift

class NavBarItem {
    typealias Callback = (() -> ())

    var title : String
    var selected: Bool
    var callback: Callback

    init(title: String, selected: Bool, callback: @escaping Callback) {
        self.title = title
        self.selected = selected
        self.callback = callback
    }
}

class NavBarButton : UIButton {
    var item : NavBarItem?
}

class NavBarView : UIView {
    var items = [NavBarItem]()
    func add(item: NavBarItem) {
        items.append(item)
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        for item in items {
            // setup the buttons properly
            let button = NavBarButton(frame: CGRect.zero)
            button.item = item
            button.addTarget(self, action: #selector(buttonTapped(sender:)), for: UIControlEvents.touchUpInside)
        }
    }

    func buttonTapped(sender: NavBarButton) {
        sender.item?.callback()
    }
}