Modifying UINavigationController corrupts navigation stack

Question

I've got a standard UINavigation controller and push my screens with push and pop as normal. However, i have one screen that switches between two view controllers on a button press so the screen flips over top reveal the other viewcontroller and visa versa. You can switch between them at will.

Now, I want the back button to work as normal so I swap the top view controller to achieve this as follows:

-(IBAction)switchToSlowProductEntry:(id)sender
{   
    NSLog(@"Switching to slow product entry");

    // Replace the top view with the findProductView
    FindProductView *findProdView = [ProductViewInstances shared].findProductView;
    NSMutableArray *views = [self.navigationController.viewControllers mutableCopy];

    [views removeLastObject];
    [views addObject:findProdView];

    // if sender is nil then assume we started from the viewDidLoad so no animation
    if(sender)
    {
        [UIView transitionWithView:self.navigationController.view duration:0.3 options:UIViewAnimationOptionTransitionFlipFromRight animations:^
        {
            [self.navigationController setViewControllers:views animated:NO];
        }
        completion:^(BOOL finished) {}];
    }
    else
        [self.navigationController setViewControllers:views animated:NO];

    NSLog(@"Views: %@", views);
    [views release];
    [ProductViewInstances shared].lastScreen = SlowProductEntryView;
}

-(IBAction)switchToQuickProductEntry:(id)sender
{
    NSLog(@"Switching to fast product entry");

    // Replace the top view with the findProductView
    QuickOrderEntryView *quickProductView = [ProductViewInstances shared].quickProductView;
    NSMutableArray *views = [self.navigationController.viewControllers mutableCopy];

    [views removeLastObject];
    [views addObject:quickProductView];

    if(sender)
    {
        [UIView transitionWithView:self.navigationController.view duration:0.3 options:UIViewAnimationOptionTransitionFlipFromLeft animations:^
         {
             [self.navigationController setViewControllers:views animated:NO];
         }
        completion:^(BOOL finished) {}];
    }
    else
        [self.navigationController setViewControllers:views animated:NO];

    NSLog(@"Views: %@", views);
    [views release];
    [ProductViewInstances shared].lastScreen = QuickProductEntryView;
}

I have a similar piece of code for the other screen. I'm using the ProductViewInstances class to maintain the two view controllers as I do not want the classes to get unloaded as I'm maintaining stage on the screen.

When you want to move forward from these screens, I do the push as normal to a new screen. It work and I go back after reviewing the products I added. If I press back I get back to the above screen and everything seems normal. However, when I press my custom back button (I need to do processing if back pressed) I run into a problem.

The popViewController does nothing. Here is the code in the base class to manage the custom back button.

-(void) viewDidLoad
{   
    self.navigationItem.leftBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:NSLocalizedString(@"Back", nil)
                                                                              style:UIBarButtonItemStyleBordered
                                                                             target:self
                                                                             action:@selector(myCustomBack)] autorelease];
    if(![ProductViewInstances shared].findProductView)
    {
        [ProductViewInstances shared].findProductView = [[FindProductView alloc] init];
        [ProductViewInstances shared].findProductView.customer = self.customer;
    }
    if(![ProductViewInstances shared].quickProductView)
    {
        [ProductViewInstances shared].quickProductView = [[QuickOrderEntryView alloc] init];
        [ProductViewInstances shared].quickProductView.customer = self.customer;
    }
}


-(void) goBack
{
    if([[ProductViewInstances shared].quickProductView checkIfItemsPending])
    {
        // Pop up dialog
        UIAlertView * alert = [[UIAlertView alloc] initWithTitle:NSLocalizedString(@"Save Entries", nil)
            message:NSLocalizedString(@"Your entries will be lost", nil)
            delegate:self
            cancelButtonTitle:NSLocalizedString(@"Cancel", nil)
            otherButtonTitles:NSLocalizedString(@"Save", nil), nil];
        [alert show];
        [alert release];
    }
    else
    {
        // Remove rows from quick item entry screen
        [[ProductViewInstances shared].quickProductView removeRowsFromtable];
        if(didPressHome)
            [self popToSpringBoard:YES];
        else
            [self.navigationController popViewControllerAnimated:YES];
    }
}

So when I press back I have to check if the entries will be lost. The pop to SpringBoard pops back a couple of screens and basically calls the following:

NSArray *controllers = appDelegate.navigationController.viewControllers;
UIViewController *springboard = [controllers objectAtIndex:2];
[appDelegate.navigationController popToViewController:springboard animated:animated];

However, the popViewController animated call does nothing... Like as if it never happened.

Donie

Answer 1

@selector(myCustomBack) will not call goBack unless you left out some code.