Alert controller which always top

TopAlertController.swift

/// Alert controller which always top. You dont need to bind it to controller.
/// Just call show method. And TopAlertController will above any controller in hierarchy.

import UIKit

// MARK: - TopAlertController

final class TopAlertController: UIAlertController {
    
    // MARK: - Private properties
   
    private lazy var alertWindow: UIWindow = {
        let window = UIWindow(frame: UIScreen.main.bounds)
        window.rootViewController = ClearViewController()
        window.backgroundColor = UIColor.clear
        window.windowLevel = UIWindow.Level.alert
        return window
    }()
    
    // MARK: - Internal methods
    
    func show(animated flag: Bool = true, completion: (() -> Void)? = nil) {
        guard let rootVC = alertWindow.rootViewController else { return }
        
        alertWindow.makeKeyAndVisible()
        rootVC.present(self, animated: flag, completion: completion)
    }
}

// MARK: - ClearViewController

fileprivate class ClearViewController: UIViewController {
    override var preferredStatusBarStyle: UIStatusBarStyle {
        UIApplication.shared.statusBarStyle
    }
    
    override var prefersStatusBarHidden: Bool {
        UIApplication.shared.isStatusBarHidden
    }
}