Adding an image to a UIAlertController

UIAlertController+Conversion.swift

extension UIAlertController {
    /// Creates a view controller for notifying the user that a conversion is occurring. Accepts a block that is executed upon conversion completion.
    static func createConvertingAlertController(onConversionCompletion: @escaping () -> Void) -> UIAlertController {
        // The title font corresponds to Dynamic Type style "Headline"
        let titleFont = UIFont.preferredFont(forTextStyle: .headline)
        let calculatorImageView = UIImageView(image: UIImage(named: "calculator.fill", in: nil, with: UIImage.SymbolConfiguration(font: UIFont.systemFont(ofSize: titleFont.pointSize * 2.0, weight: .semibold))))
        let measuringAttributedStringHeight = NSAttributedString(string: "Penguin", attributes: [.font: titleFont]).boundingRect(with: .zero, options: [.usesFontLeading, .usesLineFragmentOrigin], context: nil).height
        let desiredOffset = 15.0 + calculatorImageView.bounds.height
        let totalNewlinePrefixes = Int((desiredOffset / measuringAttributedStringHeight).rounded())
        
        let alertController = UIAlertController(title: convertingTitle(withTotalNewlines: totalNewlinePrefixes), message: "Trying to remember long division… carry the 4…", preferredStyle: .alert)
        
        let yOffset = 20.0
        calculatorImageView.frame.origin = CGPoint(x: (alertController.view.bounds.width - calculatorImageView.bounds.width) / 2.0, y: yOffset)
        calculatorImageView.autoresizingMask = [.flexibleLeftMargin, .flexibleRightMargin]
        calculatorImageView.tintColor = .secondaryLabel
        alertController.view.addSubview(calculatorImageView)
        
        let displayDurationMS = (2_500 ... 4_200).randomElement()!
        let displayDurationSeconds = TimeInterval(displayDurationMS) / 1_000
        
        let numbersTimer = Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true) { timer in
            alertController.title = convertingTitle(withTotalNewlines: totalNewlinePrefixes)
        }
        
        delay(displayDurationSeconds) {
            numbersTimer.invalidate()
            onConversionCompletion()
            alertController.dismiss(animated: true, completion: nil)
        }
        
        return alertController
    }
    
    private static func convertingTitle(withTotalNewlines totalNewlines: Int) -> String {
        let newlinePrefixes = [String](repeating: "\n", count: totalNewlines).joined()
        let numberRange = 100 ... 999
        return "\(newlinePrefixes)Converting… \(numberRange.randomElement()!)"
    }
}