Published - combine

ViewController.swift

// Create a new search subject with a default value
final class ViewController: UIViewController {
  
  // Published subject initialized to zero
  @Published var buttonTapSubject: Int = 0
  
  var cancellables = Set<AnyCancellable>()
  let button = UIButton()
  let label = UILabel()
  
  override func viewDidLoad() {
    super.viewDidLoad()
    /* layout code removed for brevity */
    
    // subscribe to button taps and assign value to label
    $buttonTapSubject
      .map{ String($0) }
      .assign(to: \.text, on: label)
      .store(in: &cancellables)
  }
  
  @objc func didTap() {
    buttonTapSubject += 1
  }
  
}