How to pass data to another controller on dismiss ViewController?

Question

I want to pass my data from one ViewController to another VC on VC dismiss. Is it possible?

I've tried the next method and no success:

On button click:

self.dismiss(animated: true) { 
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let controller = storyboard.instantiateViewController(withIdentifier: "EditViewController") as! EditViewController
        controller.segueArray = [values]
    }

when EditViewController appears again, my segueArray is nil there.

How can I pass my data from my ViewController to the EditViewController on dismiss?

Answer 1

The best way to pass data back to the previous view controller is through delegates... when going from ViewController A to B, pass view controller A as a delegate and on the viewWillDisappear method for ViewController B, call the delegate method in ViewController A.. Protocols would help define the delegate and the required methods to be implemented by previous VC. Here's a quick example:

Protocol for passing data:

protocol isAbleToReceiveData {
  func pass(data: String)  //data: string is an example parameter
} 

Viewcontroller A:

class viewControllerA: UIViewController, isAbleToReceiveData {

  func pass(data: String) { //conforms to protocol
  // implement your own implementation
   }

  prepare(for: Segue) {
    /** code for passing data **/
    let vc2 = ViewCOntrollerB()  /
    vc2.delegate = self   //sets the delegate in the new viewcontroller 
                          //before displaying
    present(vc2)
  }
}

Dismissing viewcontroller:

class viewControllerB: UIViewController {

  var delegate: isAbleToReceiveData

  viewWillDisappear {
      delegate.pass(data: "someData") //call the func in the previous vc
  }
}