在iOS中，如何在Swift的数字键盘上添加一行？

textField.keyboardType = .numberPad

let toolbar = UIToolbar()
toolbar.barStyle = .default

let flexSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
toolbar.setItems([flexSpace], animated: false)
toolbar.sizeToFit()

textField.inputAccessoryView = toolbar

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var textField: UITextField!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        textField.keyboardType = .numberPad
        
        let toolbar = UIToolbar()
        toolbar.barStyle = .default
        
        let flexSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
        toolbar.setItems([flexSpace], animated: false)
        toolbar.sizeToFit()
        
        textField.inputAccessoryView = toolbar
    }
}