如何在不打字的情况下检测UITextField光标的移动？

class ViewController: UIViewController, UITextInputDelegate {
    @IBOutlet weak var textField: UITextField!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        textField.delegate = self
    }
    
    func selectionDidChange(textInput: UITextInput?) {
        guard let textField = textInput as? UITextField else {
            return
        }
        
        let selectedRange = textField.selectedTextRange
        let startPosition = textField.offset(from: textField.beginningOfDocument, to: selectedRange?.start ?? textField.endOfDocument)
        let endPosition = textField.offset(from: textField.beginningOfDocument, to: selectedRange?.end ?? textField.endOfDocument)
        
        if startPosition != endPosition {
            // 光标发生了移动
            print("光标移动了")
        }
    }
}