What are Unwind segues for and how do you use them

Question

iOS 6 and Xcode 4 5 has a new feature referred to as  Unwind Segue       Unwind segues can allow transitioning to existing instances of scenes in a storyboard   In addition to this brief entry in Xcode 4 5 s release notes  UIViewController now seem to have a couple of new methods   -  BOOL canPerformUnwindSegueAction  SEL action fromViewController  UIViewController   fromViewController withSender  id sender -  UIViewController   viewControllerForUnwindSegueAction  SEL action fromViewController  UIViewController   fromViewController withSender  id sender -  UIStoryboardSegue   segueForUnwindingToViewController  UIViewController   toViewController fromViewController  UIViewController   fromViewController identifier  NSString   identifier   How do unwind segues work and what they can be used for

User · Answer

Swift iOS   Step 1  define this method into your MASTER controller view  in which you want to go back     pragma mark - Unwind Seques  IBAction func goToSideMenu segue  UIStoryboardSegue         println  Called goToSideMenu  unwind action        Step 2   StoryBoard  Right click on you SLAVE CHILD EXIT button and Select  goToSideMenu  As action to Connect you Button on which you will click to return back to you MASTER controller view    step 3  Build and Run

User · Answer

In a Nutshell  An unwind segue  sometimes called exit segue  can be used to navigate back through push  modal or popover segues  as if you popped the navigation item from the navigation bar  closed the popover or dismissed the modally presented view controller   On top of that you can actually unwind through not only one but a series of push modal popover segues  e g   go back  multiple steps in your navigation hierarchy with a single unwind action   When you perform an unwind segue  you need to specify an action  which is an action method of the view controller you want to unwind to   Objective-C   -  IBAction unwindToThisViewController  UIStoryboardSegue   unwindSegue       Swift    IBAction func unwindToThisViewController segue  UIStoryboardSegue        The name of this action method is used when you create the unwind segue in the storyboard  Furthermore  this method is called just before the unwind segue is performed  You can get the source view controller from the passed UIStoryboardSegue parameter to interact with the view controller that initiated the segue  e g  to get the property values of a modal view controller   In this respect  the method has a similar function as the prepareForSegue  method of UIViewController   iOS 8 update  Unwind segues also work with iOS 8 s adaptive segues  such as Show and Show Detail   An Example  Let us have a storyboard with a navigation controller and three child view controllers     From Green View Controller you can unwind  navigate back  to Red View Controller  From Blue you can unwind to Green or to Red via Green  To enable unwinding you must add the special action methods to Red and Green  e g  here is the action method in Red   Objective-C    implementation RedViewController  -  IBAction unwindToRed  UIStoryboardSegue   unwindSegue       end   Swift    IBAction func unwindToRed segue  UIStoryboardSegue        After the action method has been added  you can define the unwind segue in the storyboard by control-dragging to the Exit icon  Here we want to unwind to Red from Green when the button is pressed     You must select the action which is defined in the view controller you want to unwind to     You can also unwind to Red from Blue  which is  two steps away  in the navigation stack   The key is selecting the correct unwind action   Before the the unwind segue is performed  the action method is called  In the example I defined an unwind segue to Red from both Green and Blue  We can access the source of the unwind in the action method via the UIStoryboardSegue parameter   Objective-C   -  IBAction unwindToRed  UIStoryboardSegue   unwindSegue       UIViewController  sourceViewController   unwindSegue sourceViewController       if   sourceViewController isKindOfClass  BlueViewController class                  NSLog   Coming from BLUE               else if   sourceViewController isKindOfClass  GreenViewController class                  NSLog   Coming from GREEN               Swift    IBAction func unwindToRed unwindSegue  UIStoryboardSegue        if let blueViewController   unwindSegue sourceViewController as  BlueViewController           println  Coming from BLUE             else if let redViewController   unwindSegue sourceViewController as  RedViewController           println  Coming from RED             Unwinding also works through a combination of push modal segues  E g  if I added another Yellow view controller with a modal segue  we could unwind from Yellow all the way back to Red in a single step     Unwinding from Code  When you define an unwind segue by control-dragging something to the Exit symbol of a view controller  a new segue appears in the Document Outline     Selecting the segue and going to the Attributes Inspector reveals the  Identifier  property  Use this to give a unique identifier to your segue     After this  the unwind segue can be performed from code just like any other segue   Objective-C    self performSegueWithIdentifier   UnwindToRedSegueID  sender self     Swift   performSegueWithIdentifier  UnwindToRedSegueID   sender  self

User · Answer

As far as how to use unwind segues in StoryBoard     Step 1    Go to the code for the view controller that you wish to unwind to and add this   Objective-C  -  IBAction unwindToViewControllerNameHere  UIStoryboardSegue   segue         nothing goes here     Be sure to also declare this method in your  h file in Obj-C  Swift   IBAction func unwindToViewControllerNameHere segue  UIStoryboardSegue          nothing goes here     Step 2    In storyboard  go to the view that you want to unwind from and simply drag a segue from your button or whatever up to the little orange  EXIT  icon at the top right of your source view     There should now be an option to connect to  - unwindToViewControllerNameHere   That s it  your segue will unwind when your button is tapped

User · Answer

Something that I didn t see mentioned in the other answers here is how you deal with unwinding when you don t know where the initial segue originated  which to me is an even more important use case  For example  say you have a help view controller  H  that you display modally from two different view controllers  A and B    A   H B   H  How do you set up the unwind segue so that you go back to the correct view controller  The answer is that you declare an unwind action in A and B with the same name  e g       put in AViewController swift and BViewController swift  IBAction func unwindFromHelp sender  UIStoryboardSegue           empty     This way  the unwind will find whichever view controller  A or B  initiated the segue and go back to it   In other words  think of the unwind action as describing where the segue is coming from  rather than where it is going to

User · Answer

Unwind segues are used to  go back  to some view controller from which  through a number of segues  you got to the  current  view controller   Imagine you have something a MyNavController with A as its root view controller  Now you use a push segue to B  Now the navigation controller has A and B in its viewControllers array  and B is visible  Now you present C modally   With unwind segues  you could now unwind  back  from C to B  i e  dismissing the modally presented view controller   basically  undoing  the modal segue  You could even unwind all the way back to the root view controller A  undoing both the modal segue and the push segue   Unwind segues make it easy to backtrack  For example  before iOS 6  the best practice for dismissing presented view controllers was to set the presenting view controller as the presented view controller   s delegate  then call your custom delegate method  which then dismisses the presentedViewController  Sound cumbersome and complicated  It was  That   s why unwind segues are nice

User · Answer

For example if you navigate from viewControllerB to viewControllerA then in your viewControllerA below delegate will call and data will share    IBAction func unWindSeague    sender   UIStoryboardSegue                    if sender source is ViewControllerB                              if let     sender source as  ViewControllerB                                   self textLabel text    Came from B   B- gt A   B exited                                                                             Unwind Seague Source View Controller   You Need to connect Exit Button to VC   s exit icon and connect it to unwindseague       Unwind Seague Completed -  TextLabel of viewControllerA  is Changed

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

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