How to find the view controller responsible for a view

If you need to find the view controller that is responsible for a particular view, the easiest thing to do is walk the responder chain. This chain is built into all iOS apps, and lets you walk from one view up to its parent view, its grandparent view, and so on, until it reaches a view controller. You can even carry on going if you want, up through parent view controllers and ultimately to the app delegate.
To try it out, add this extension to UIView to your code:

extension UIView {
    func findViewController() -> UIViewController? {
        if let nextResponder = self.next as? UIViewController {
            return nextResponder
        } else if let nextResponder = self.next as? UIView {
            return nextResponder.findViewController()
        } else {
            return nil
        }
    }
}

You can now call findViewController() on any view, and you’ll get back nil or its view controller.