How to check in UISlider function which Button is selected

ViewController.swift

/**
 * be sure that the slider's continuous property is also set. 
 * On the other hand, if you don't want the event to fire as the user is sliding and only when they finish sliding, 
 * set continuous to NO (or uncheck in IB)
 */

class ViewController: UIViewController {
  @IBOutlet weak var slider: UISlider!
  override func viewDidLoad() {
    super.viewDidLoad()
    /// add on value change listner
    self.slider.addTarget(self, action: #selector(sliderDidChange(_:)), for: .valueChanged)
  }

  /// on value change function
  @objc
  func sliderDidChange(_ sender: UISlider) {
    // check button value here then update the wanted UILabel
  }
}