Modifying UINavigationController corrupts navigation stack - ios

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.