unwind segue not triggering

Question

I have been learning swift and have made the foundation of most of my app. I have the following storyboard

app storyboard

Everything works fine. For example

Answer 1

Like Craig in the comments said, it's not that easy to find the problem. So I just build a simple app where you can follow the steps as guide and see if you forgot something to setup the functionality right. Hope it will help you. Note: Code is in Swift 3.0, but should be easy to adopt to 2.*

1. Storyboard with two View Controllers:

2. Declare the action method for the unwind segue in the FirstViewController.swift:

class FirstViewController: UIViewController {
  // action method for the unwind segue
  @IBAction func updateScore(_ segue: UIStoryboardSegue) {
    print("Back in the FirstViewController")
  } 
}

3. Connect the Save button in the Storyboard with the action method (with ctrl + drag):

4. Connect your Save button with the SecondViewController.swift file, to use it for checking in your prepareSegue method (with ctrl + drag):

5. Add the prepare(for:sender:) method to your SecondViewController.swift:

class SecondViewController: UIViewController {

  @IBOutlet weak var saveButtonPressed: UIBarButtonItem!

  override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    // check safely with guard that your save button is the sender and you can use it
    // if not print message
    guard let uiBarButtonItem = sender as? UIBarButtonItem else {
      print("There is no UIBarButtonItem sender")
      return
    }

    // check if you selected the save button
    if saveButtonPressed == uiBarButtonItem {
      print("save button selected")
    }
  }
}

Result:

The sample app you can find here

Answer 2

I did not manage to get the unwind segue to work but instead used

navigationController!.popViewControllerAnimated(true)

as a work around and this works fine.