Weird custom segue behavior - Navigation stack corruption

Question

I have a big application with many transitions in it using storyboard. The transitions should be from right to left so I made a custom segue to perform it.

When I use the regular transition, each view controller I push into the navigation stack is being retained until I pop it.

While using custom segues doesn't retain the previous controller (the one who push the current controller) and when I pop back, the instance of the controller gets a different memory address, which indicates that the pointer had changed.

This is the custom push segue:

UIViewController *sourceViewController = (UIViewController*)[self         sourceViewController];
UIViewController *destinationController = (UIViewController*)[self   destinationViewController];

CATransition* transition = [CATransition animation];
transition.duration = .3f;
transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
transition.type = kCATransitionPush;
transition.subtype = kCATransitionFromLeft;

[sourceViewController.navigationController.view.layer addAnimation:transition
                                                            forKey:kCATransition];

[sourceViewController.navigationController pushViewController:destinationController animated:NO];

and the custom pop segue:

UIViewController *sourceViewController = (UIViewController*)[self sourceViewController];
UIViewController *destinationController = (UIViewController*)[self destinationViewController];

CATransition* transition = [CATransition animation];
transition.duration = .3f;
transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
transition.type = kCATransitionPush;
transition.subtype = kCATransitionFromRight;

[sourceViewController.navigationController.view.layer addAnimation:transition
                                                            forKey:kCATransition];

[sourceViewController.navigationController pushViewController:destinationController animated:NO];

I perform the the segue with this method:

[self performSegueWithIdentifier:@"SearchToMenu" sender:self];

Nothing seems to work and I haven't found anything online.

If I need to provide more code examples, screenshots, etc, please let me know.

foundry foundry · Accepted Answer · 2012-12-20T02:28:34

Your popViewController is pushing, not popping.

This line:

 [sourceViewController.navigationController pushViewController:destinationController animated:NO];

should be:

[sourceViewController.navigationController popViewControllerAnimated:NO];

Your custom segue does retain the previous controller. But the destinationController of a segue is always a freshly instantiated object. You noticed that you were getting a different memory address for the new controller, but if you check your [self.navigationController viewControllers] stack you will see that the original viewController was still there, three objects down on the stack. In this corrected version you will return to that instance of the viewContoller, as you intend.

That's why you should never use a standard push segue to navigate back to anywhere lower down on your stack. Although the Storyboard will suggest that this is what will happen, it's illusory: your are just navigating ON to a new instance of the previous viewController's class. It will look exactly like the previous one in it's initial state, because it is using the same Storyboard layout.

Yours is a good example case where it might be better not to use a segue at all. It is not only confusing at this point, but, when you are popping back, if you were to try to configure the "destinationViewController" in prepareForSegue it would have no effect on your popped-back-to viewController. You may also have noticed that the Storyboard gets messed up, as it loses track of which viewController is contained in which NavController. You lose the navBars and the ability to configure them at all (in the storyboard - they are still there in the app).

Weird custom segue behavior - Navigation stack corruption

1 Answers