How to call non-static method from static method of the viewController class in swift?

Question

Hello I would like to know how to call a non static method from static method in the UIViewController class.

what i did is:

 public static func cambiarPosicion(posicion: Int){

    var reserva :   ReservaViewController = ReservaViewController()

    reserva.cambiarContainer(posicion: posicion)

} 

But for calling the method that I want in the UIViewController I have created a instance of the same viewController(ReservaViewController) as you see. Then I used it for call a method called cambiarContainer but I have a problem in that method, the error is:

Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

and some code that I have in that method and where I have the error is:

self.btnSelectUbicacion.setBackgroundImage(#imageLiteral(resourceName: 
    "fondo_transparente"), for: .normal)
self.btnSelectServicio.setBackgroundImage(nil, for: .normal)
self.btnSelectHora.setBackgroundImage(#imageLiteral(resourceName: 
  "fondo_transparente"), for: .normal)
self.btnConfirmacionReserva.setBackgroundImage(#imageLiteral(resourceName: 
  "fondo_transparente"), for: .normal)

The error is in the first line I think that this problem is because I am calling the method from another instance, it is for that reason that I would like to know how to call a non method static from a static method.

Answer 1

Because a static field/method--by definition--is not tied to any single object/instance of the class, while a non-static field/method always refers to an actual object/instance in some way.

So, you can't call non static method inside static method.

Answer 2

Think of a class as a factory. Say we have a Car class. The class is the factory that makes the cars. An instance of a Car is an actual car, in a specific color, with a license tag, that belongs to somebody.

You can tell an instance of car to set its radio to a given station. It doesn't make sense to do that from the factory however. ("Hey car factory, set the radio on Bob's car to 'Hits 101'").

Answer 3

If you use storyboard or.xib file with UIViewController, you should create the controller with create its storyboard or.xib:

with.xib file:

ViewController(nibName: "ViewController", bundle: nil)

with.storyBoard:

 let storyboard = UIStoryboard(name: "storyboardName", bundle: nil)
 let controller = storyboard.instantiateViewController(withIdentifier: "ViewControllerIdentifier")