Swift - Unwind Segue triggering error - ios

Question

I am using for the first time the Unwind Segue approach. I have multiple view controllers as can be seen in the picture below (a few of them shown of course). In the Edit Profile I have a Done button. Once clicked I trigger an IBAction that triggers an unwind segue.
Here is the code for the Done button in the nav bar:
#IBAction func unwindToMainViews(sender: UIStoryboardSegue) {
//let sourceViewController = sender.sourceViewController
self.performSegueWithIdentifier("unwindToMainSegue", sender: self)
}
and in the
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!)
I am doing the following to pass data from Edit Profile back to Home View
if (segue.identifier == "unwindToMainSegue") {
// pass data to next view
let tabCtrl = segue.destinationViewController as! UITabBarController
let destinationVC = tabCtrl.viewControllers![0] as! HomeViewController
destinationVC.userObject = self.userObject;
}
When segue identifier is matched and code is executed (to transfer userObject from this controller to another), it triggers the error:
Could not cast value of type 'app.EditProfileViewController' (0x100b99d80) to 'UITabBarController' (0x104a1d030).
How can this error be fixed? I am surprised since i am casting to UITabBarController so thought it should work.

Answer 1

You don't return to the UITabBarController in an unwind segue. You return to the ViewController that triggered the original segue, or one if its ancestors.
As #jlehr stated in the comments:
Unwind segues don't return to anything; they dismiss any pushed and
presented view controllers between the source and destination view
controller. The destination is wherever the implementation of the
unwind method is found, regardless of how the source view controller
was presented.
To unwind to the viewController that triggered the original segue, you need to implement the #IBAction func returnToHere(segue: UIStoryboardSegue) function in the viewController you want to return to.
Then when you set up your Done button by dragging to the Exit icon, you select returnToHere from the pop-up.
To pass data back to the sourceViewController, give your unwind segue an identifier such as "unwindToSource", then override prepareForSegue in the viewController you are returning from:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "unwindToSource" {
let dvc = segue.destinationViewController as! SourceViewController
dvc.userObject = self.userObject
}
}