create alert function in all view controllers - swift

Question

I'm trying to declare a function for showing alerts in my app. To avoid repeating work, i'm trying to use same function for all my app. I tried to do that by creating a class with function showNotification. but when i create an object of that class and call the method, nothing happens. How can i do that?

class SharedPropertiesAndMetods : UIViewController {

    func showNotification(title: String, message: String)
    {
        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
        let defaultAction = UIAlertAction(title: "تائید", style: .default, handler: nil)
        alertController.addAction(defaultAction)
        present(alertController, animated: true, completion: nil)
    }

}

Answer 1

Use an extension like this

extension UIViewController {
  func showAlert(title: String, message: String) {
    let alertController = UIAlertController(title: title, message:
      message, preferredStyle: .alert)
    alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: {action in
    }))
    self.present(alertController, animated: true, completion: nil)
  }
}

call the function like this

self.showAlert(title: "hi", message: "test")

Answer 2

What I would do is to create a 'generic' view controller that do the job and than inherit from it:

1. If you want to display alert each time view did appear:

class GenericViewController: UIViewController {

    // MARK: - View lifecycle -

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        if let notification = self.shouldDisplayAlertNotification() {
            self.showNotification(notification)
        }
    }

    // MARK: - Internal methods -

    func shouldDisplayAlertNotification() -> AlertNotification? {
        return nil
    }

    // MARK: - Private methods -

    private func showNotification(_ alertNotification: AlertNotification) {
    }

}

class MyController: GenericViewController {

    override func shouldDisplayAlertNotification() -> AlertNotification? {
        return AlertNotification(title: "Title", message: "Message")
    }

}

Where AlertNotification is your custom model class:

class AlertNotification {
    var title: String
    var message: String

    init(title: String, message: String) {
        self.title = title
        self.message = message
    }
}

In this way, only VC that overrides shouldDisplayAlertNotificationwill display alert.

2. If you want to display alert on 'demand':

As suggested, extend UIViewController

extension UIViewController {
    func showNotification(title: String, message: String) {
    }
}