How to determine which textfield is active swift

Question

I cant figure out which UITextField is currently active so i can clear its text if they hit cancel on a UIBarButtonItem. Here is my code. There is

Answer 1

In order to improve @Reimond's answer Swift 4

extension UIView {
    var textFieldsInView: [UITextField] {
        return subviews
            .filter ({ !($0 is UITextField) })
            .reduce (( subviews.compactMap { $0 as? UITextField }), { summ, current in
                return summ + current.textFieldsInView
        })
    }
    var selectedTextField: UITextField? {
        return textFieldsInView.filter { $0.isFirstResponder }.first
    }
}

usage:

view.selectedTextField