How to move to existing viewcontroller from another viewcontroller

Question

When I start the app my initial view is MainViewController.
Then on button click I move to AnotherViewController.

performSegueWithIdentifier("myFirstSegue", sender: self)

On AnotherViewController I have a button that should return me back to MainViewController but I don't want to instantiate new but to use existing instance.

let storyboard = UIStoryboard(name: "Main", bundle: nil)
var story = storyboard.instantiateViewControllerWithIdentifier("MainViewController") as! ViewController
let navigationController = UINavigationController(rootViewController: story)
self.showViewController(navigationController, sender: nil)

With this code I create new so I lost data that I stored on that view.

How can I get existing instance and just move to it?

UPDATE

To explain issue better if on first view I have UISwitch and move to another ViewController and then get back to first I want to UISwitch stay same not "reset".

Answer 1

if you are using a navigation controller, doing this will pop to your previous controller. navigationController.popViewControllerAnimated(true)

Answer 2

you can use this one

self.dismissViewControllerAnimated(false, completion: nil);

Answer 3

Navigation controller maintains the stack of viewcontrollers. just pop your viewcontroller and you will be back to your previous view controller.

navigationController.popViewControllerAnimated(true)

or use unwind segue from storyboard.

What are Unwind segues for and how do you use them?