Ios 使用选择器查看选定的行文本

我只想通过如下调用获取UIPickerView中选定行的字符串值：

let myString = getString(from: myPickerView, inComponent: 0)

我尝试过像这样扩展UIPickerViewDelegate类：

extension UIPickerViewDelegate {

    func getString(from pickerView: UIPickerView, inComponent component: Int) -> String {
        return pickerView(pickerView, titleForRow: pickerView.selectedRow(inComponent: component), forComponent: component)
    }

}

但我得到一个错误：

“无法调用非函数类型'UIPickerView'的值”

---

当我替换以下内容时，它会起作用：

func getString(from pickerView: UIPickerView, inComponent component: Int) -> String {
   return pickerView(pickerView, titleForRow: pickerView.selectedRow(inComponent: component), forComponent: component)
}

作者：

func getString(from picker: UIPickerView, inComponent selectedComponent: Int) -> String? {
    return pickerView!(picker, titleForRow: picker.selectedRow(inComponent: selectedComponent), forComponent: selectedComponent)
}