import UIKit


public extension UIViewController{

    class func instantiate<T: UIViewController>() -> T {

        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let identifier = String(describing: self)
        return storyboard.instantiateViewController(withIdentifier: identifier) as! T
    }




    @discardableResult func showAlert(title: String?, message: String?, buttonTitles: [String]? = nil, highlightedButtonIndex: Int? = nil, completion: ((Int) -> Void)? = nil) -> UIAlertController {
        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
        var allButtons = buttonTitles ?? [String]()
        if allButtons.count == 0 {
            allButtons.append("OK")
        }

        for index in 0..<allButtons.count {
            let buttonTitle = allButtons[index]
            let action = UIAlertAction(title: buttonTitle, style: .default, handler: { (_) in
                completion?(index)
            })
            alertController.addAction(action)
            // Check which button to highlight
            if let highlightedButtonIndex = highlightedButtonIndex, index == highlightedButtonIndex {
                if #available(iOS 9.0, *) {
                    alertController.preferredAction = action
                }
            }
        }
        present(alertController, animated: true, completion: nil)
        return alertController
    }
}