LeakInspectorAlertProvider.swift

import UIKit

@objc class LeakInspectorAlertProvider: NSObject, LeakInspectorDelegate {

    private weak var alertController: UIAlertController?

    func didLeakReference(_ ref: AnyObject, name: String) {
        // dismiss any already visible alert
        if let alertController = self.alertController {
            alertController.dismiss(animated: false, completion: nil)
        }

        let title = "Leak Inspector"
        let message = "Detected possible leak of \(name)"
        let ok = "OK"

        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
        alertController.addAction(UIAlertAction(title: ok, style: .default, handler: nil))
        alertController.show()
        self.alertController = alertController
    }

}

extension UIAlertController {

    func show() {
        present(animated: true, completion: nil)
    }

    func present(animated: Bool, completion: (() -> Void)?) {
        let keyWindow: UIWindow? = {
            if #available(iOS 13, *) {
                return UIApplication.shared.windows.first { $0.isKeyWindow }
            } else {
                return UIApplication.shared.keyWindow
            }
        }()
        if let rootVC = keyWindow?.rootViewController {
            present(from: rootVC, animated: animated, completion: completion)
        }
    }

    private func present(from controller: UIViewController, animated: Bool, completion: (() -> Void)?) {
        if let presentedViewController = controller.presentedViewController {
            present(from: presentedViewController, animated: animated, completion: completion)
        } else if  let navVC = controller as? UINavigationController, let visibleVC = navVC.visibleViewController {
            present(from: visibleVC, animated: animated, completion: completion)
        } else if let tabVC = controller as? UITabBarController, let selectedVC = tabVC.selectedViewController {
            present(from: selectedVC, animated: animated, completion: completion)
        } else {
            controller.present(self, animated: animated, completion: completion)
        }
    }
    
}