遍历一个控件中的所有子控件，可以使用递归的思想
func find(view: AnyClass, inView: UIView, finished: @escaping (_ view: UIView) -> Void) {
for subview in inView.subviews {
if subview.isKind(of: view.self) {
finished(subview)
}
find(view: view, inView: subview, finished: finished)
}
}
使用
find(view: UITextField.self, inView: self) { (view) in
// view is UITextField
}
