UIPickerView获取没有数据源的选定值

import UIKit

class ViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {

    let pickerView = UIPickerView()
    let textField = UITextField()
    var selectedValue: String?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        pickerView.delegate = self
        pickerView.dataSource = self
        
        textField.inputView = pickerView
        view.addSubview(textField)
    }
    
    // UIPickerViewDataSource协议方法，返回选择器的列数
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }
    
    // UIPickerViewDataSource协议方法，返回每一列的行数
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return 0 // 不展示数据，所以返回0
    }
    
    // UIPickerViewDelegate协议方法，用户选择了某一行时调用
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        selectedValue = "选中的值为：\(row)"
        textField.text = selectedValue
    }
}