!UIView+ForEach.swift

extension UIView {
    func forEachSubviewOfType<V: UIView>(type: V.Type, @noescape apply block: V -> Void) {
        for view in subviews {
            if let view = view as? V {
                block(view)
            } else {
                view.forEachSubviewOfType(V.self, apply: block)
            }
        }
    }
}

Example.swift

searchController.searchBar.forEachSubviewOfType(UITextField.self) { textField in
    textField.textColor = .whiteColor()
}