Perform segue after unwinding - xcode

Question

I have a main screen wrapped in a navigation controller.
The main screen has several buttons that trigger segues to other views. One button goes to a table view.
A selection in this table should trigger a segue that is normally performed by one of the buttons on the main view.
I was assuming that I need to unwind to the main screen first, and then trigger a segue from the unwind segue programmatically, but what happens when I do that is that it performs the programmatic segue first, then unwinds, and ends up on the main screen again.
What is the correct way to deal with this situation? I don't want to be able to go back to the table view after the programmatically called segue, the back button should then go to the main view.
In case it helps to explain my use case a little more: The table view is a list of levels. A selection should launch my game view with the level picked in the table view.
My unwind segue in my main view:
#IBAction func backFromLevelSelectionUnwindSegue(segue:UIStoryboardSegue) {
performSegueWithIdentifier("playSegue", sender: self)
}
obviously playSegue is the segue to the game view controller.
An answer to a similar question suggests setting a boolean flag and then performing the segue in viewDidAppear, but it seems like that viewDidAppear should not have to know about an unwind segue that has occurred. Is there a "correct" solution that I haven't come across?

Answer 1

In your backFromLevelSelectionUnwindSegue, your are still in a unwind segue context. So call performSegueWithIdentifier after the context finished using dispatch_async or performSelector:withObject:afterDelay like below.
#IBAction func
backFromLevelSelectionUnwindSegue( segue:UIStoryboardSegue ) {
dispatch_async( dispatch_get_main_queue() ) {
self.performSegueWithIdentifier( "playSegue", sender: self )
}
}

Answer 2

Would it be possible for you to perform a segue to the game view without unwinding it to the main screen? Then when you unwind the segue, unwind it to the main view instead of back to table view? If I remember correctly, we are able to unwind past the presenting view controller.

Answer 3

This is a matter of opinion, but in your case I think you should simply have a segue between the tableview and the game, with any extra data necessary being passed to the tableview VC from the main VC.
If you need go back multiple viewControllers in a UINavigationVC, I would look at using popToRootViewController or use an unWind between them. e.g. call unwind from the 3rd viewController, with the handler in the 1st viewController

Answer 4

It's possible to have multiple unwind segues that go back to different places. In the scenario given the view controllers should be arranged Main->LevelSelect->Game
and then when game ends you have buttons for 2 or 3 unwind segues. First one is exitToGameStart that allows the player to restart the same level. exitToLevelSelect allows player to choose a new level. And optionally exitToMainMenu goes all the way back to the start. For a full example, see Apple's UnwindSegue sample, and in particular the "Start Over" button on the last table that performs the exitToQuizStart unwind segue and the "Return To The Menu Screen" that performs the exitToHomeScreen unwind segue. Code for the receiving methods are below:
QuestionViewController.m
//! Unwinds from the ResultsViewController back to the first
//! QuestionViewController when the user taps the 'Start Over' button.
//
// This is an unwind action. Note that the sender parameter is a
// 'UIStoryboardSegue*' instead of the usual 'id'. Like all unwind actions,
// this method is invoked early in the unwind process, before the visual
// transition. Note that the receiver of this method is the
// destinationViewController of the segue. Your view controller should use
// this callback to update its UI before it is redisplayed.
//
- (IBAction)exitToQuizStart:(UIStoryboardSegue *)sender
{
// The user has restarted the quiz.
[self.currentQuiz resetQuiz];
}
MainMenuViewController.m
//! Unwinds from the ResultsViewController back to the MainMenuViewController
//! when the user taps the 'Return to the Home Screen' button.
//
// This is an unwind action. Note that the sender parameter is a
// 'UIStoryboardSegue*' instead of the usual 'id'. Like all unwind actions,
// this method is invoked early in the unwind process, before the visual
// transition. Note that the receiver of this method is the
// destinationViewController of the segue. Your view controller should use
// this callback to retrieve information from the sourceViewController. Used
// properly, this method can replace existing delegation techniques for
// passing information from a detail view controller to a previous view
// controller in the navigation hierarchy.
//
- (IBAction)exitToHomeScreen:(UIStoryboardSegue *)unwindSegue
{
// Retrieve the score from the ResultsViewController and update the high
// score.
ResultsViewController *resultVC = (ResultsViewController*)unwindSegue.sourceViewController;
self.highScore = MAX(resultVC.currentQuiz.percentageScore, self.highScore);
}
Note: to build the old project in the latest Xcode, open the storyboard, file inspector, builds for, pick a newer iOS version.