在UITextField中显示右视图和清除按钮

func textFieldDidBeginEditing(_ textField: UITextField) {
    let clearButton = UIButton(type: .custom)
    clearButton.setImage(UIImage(named: "clear_icon"), for: .normal)
    clearButton.frame = CGRect(x: 0, y: 0, width: 20, height: 20)
    clearButton.addTarget(self, action: #selector(clearButtonTapped), for: .touchUpInside)
    textField.rightView = clearButton
    textField.rightViewMode = .whileEditing
}

@objc func clearButtonTapped(_ sender: UIButton) {
    textField.text = ""
}