swift how change UIAlertController font

Question

When I added an extension to UIAlertController to modify actions fonts, it didn't seem to work. What should I do to modify the Action font。 Here is my code

extension UIAlertController {
   
    open override func viewDidLayoutSubviews() {
       super.viewDidLayoutSubviews()
       
       if self.preferredStyle == .actionSheet {
           for i in self.actions {
               let attributedText = NSAttributedString(string: i.title ?? "", attributes: [NSAttributedString.Key.font : UIFont(name: "SFProText-Semibold", size: 15.0)!])
               
               guard let label = (i.value(forKey: "__representer") as AnyObject).value(forKey: "label") as? UILabel else { return }
                          label.attributedText = attributedText
           }
       }
       
   }
}

Answer 1

Create an extension of UIAlertController

extension UIAlertController {
    
  func setBackgroudColor(color: UIColor) {
    if let bgView = self.view.subviews.first,
      let groupView = bgView.subviews.first,
      let contentView = groupView.subviews.first {
      contentView.backgroundColor = color
    }
  }

  func setTitle(font: UIFont?, color: UIColor?) {
    guard let title = self.title else { return }
    let attributeString = NSMutableAttributedString(string: title)
    if let titleFont = font {
      attributeString.addAttributes([NSAttributedString.Key.font : titleFont],
        range: NSMakeRange(0, title.utf8.count))
    }
    if let titleColor = color {
      attributeString.addAttributes([NSAttributedString.Key.foregroundColor : titleColor],
        range: NSMakeRange(0, title.utf8.count))
    }
    self.setValue(attributeString, forKey: "attributedTitle")
  }

  func setMessage(font: UIFont?, color: UIColor?) {
    guard let title = self.message else {
      return
    }
    let attributedString = NSMutableAttributedString(string: title)
    if let titleFont = font {
      attributedString.addAttributes([NSAttributedString.Key.font : titleFont], range: NSMakeRange(0, title.utf8.count))
    }
    if let titleColor = color {
      attributedString.addAttributes([NSAttributedString.Key.foregroundColor : titleColor], range: NSMakeRange(0, title.utf8.count))
    }
    self.setValue(attributedString, forKey: "attributedMessage")
  }

  func setTint(color: UIColor) {
    self.view.tintColor = color
  }
}

Call it from a UIViewController may be in a button action like below.

func tapShowAlert() {
    let alertController = UIAlertController(title: "Alert!!", message: "This is custom alert message", preferredStyle: .alert)
    alertController.setTitle(font: UIFont.boldSystemFont(ofSize: 24), color: UIColor.yellow)
    alertController.setMessage(font: UIFont(name: "Verdana", size: 16), color: UIColor.red)
    let actnOk = UIAlertAction(title: "Ok", style: .default, handler: nil)
    let actnCancel = UIAlertAction(title: "Cancel", style: .default, handler: nil)
    alertController.addAction(actnOk)
    alertController.addAction(actnCancel)
    self.present(alertController, animated: true, completion: nil)
}