In my viewDidAppear, how do I know when it's being unwound by a child?

Question

When my child performs an unwind segue, my controller's viewDidAppear gets called.

In this method (and this method alone, I need to know whether it was from an unwind or not)

Note: the child is unwinding to the very first view controller, so this is an intermediate view controller, not the true root.

Answer 1

You should be able to use the following to detect in each controller if the exposure of the view controller was as a result of being pushed/presented, or as a result of being exposed as a result of pop/dismiss/unwind.

This may or may be enough for your needs.

- (void) viewDidAppear:(BOOL)animated{     [super viewDidAppear:animated];      // Handle controller being exposed from push/present or pop/dismiss     if (self.isMovingToParentViewController || self.isBeingPresented){         // Controller is being pushed on or presented.     }     else{         // Controller is being shown as result of pop/dismiss/unwind.     } } 

If you want to know that viewDidAppear was called because of an unwind segue as being different from a conventional pop/dismiss being called, then you need to add some code to detect that an unwind happened. To do this you could do the following:

For any intermediate controller you want to detect purely an unwind in, add a property of the form:

/** BOOL property which when TRUE indicates an unwind occured. */ @property BOOL unwindSeguePerformed; 

Then override the unwind segue method canPerformUnwindSegueAction:fromViewController:withSender: method as follows:

- (BOOL)canPerformUnwindSegueAction:(SEL)action                  fromViewController:(UIViewController *)fromViewController                          withSender:(id)sender{   // Set the flag indicating an unwind segue was requested and then return   // that we are not interested in performing the unwind action.   self.unwindSeguePerformed = TRUE;    // We are not interested in performing it, so return NO. The system will   // then continue to look backwards through the view controllers for the    // controller that will handle it.   return NO; } 

Now you have a flag to detect an unwind and a means to detect the unwind just before it happens. Then adjust the viewDidAppear method to include this flag.

- (void) viewDidAppear:(BOOL)animated{     [super viewDidAppear:animated];      // Handle controller being exposed from push/present or pop/dismiss     // or an unwind     if (self.isMovingToParentViewController || self.isBeingPresented){         // Controller is being pushed on or presented.         // Initialize the unwind segue tracking flag.         self.unwindSeguePerformed = FALSE;     }     else if (self.unwindSeguePerformed){         // Controller is being shown as a result of an unwind segue     }     else{         // Controller is being shown as result of pop/dismiss.     } } 

Hopefully this meets your requirement.

For docs on handling the unwind segue chain see: https://developer.apple.com/library/ios/technotes/tn2298/_index.html