PushPopNotifyingNavigationController. Add new notifications to UINavigationController, for when interested in when a view is specifically pushed or popped, instead of the normal delegate method which are called when views are revealed in either manner indistinguishably.

PushPopNotifyingNavigationController.h

//
//  PushPopNotifyingNavigationController.h
//  
//
//  Created by Pierre Houston on 2013-07-29.
//
// Add new notifications to UINavigationController, for when interested in when a
// view is specifically pushed or popped, instead of the normal delegate method
// which are called when views are revealed in either manner indistinguishably.

#import <UIKit/UIKit.h>

@interface PushPopNotifyingNavigationController : UINavigationController
// the previously shown view controller, nil when first opened, o/w the parent when pushed, or the just popped child
@property (nonatomic, readonly) UIViewController *previousViewController;
@end

@protocol PushPopNotifyingNavigationControllerDelegate <UINavigationControllerDelegate>
@optional
- (void)navigationController:(UINavigationController *)navigationController willPushViewController:(UIViewController *)pushedViewController;
- (void)navigationController:(UINavigationController *)navigationController willPushViewController:(UIViewController *)pushedViewController onto:(UIViewController *)coverredViewController;

- (void)navigationController:(UINavigationController *)navigationController willPopViewController:(UIViewController *)poppedViewController;
- (void)navigationController:(UINavigationController *)navigationController willPopViewController:(UIViewController *)poppedViewController backTo:(UIViewController *)revealedViewController;
- (void)navigationController:(UINavigationController *)navigationController isPoppingViewController:(UIViewController *)poppedViewController;
- (void)navigationController:(UINavigationController *)navigationController isPoppingViewController:(UIViewController *)poppedViewController backTo:(UIViewController *)revealedViewController;
@end

PushPopNotifyingNavigationController.m

//
//  PushPopNotifyingNavigationController.m
//  
//
//  Created by Pierre Houston on 2013-07-29.
//
// Add new notifications to UINavigationController, see http://stackoverflow.com/questions/642312/
// To do: also override popToViewController:animated & popToRootViewControllerAnimated:

#import "PushPopNotifyingNavigationController.h"

@implementation PushPopNotifyingNavigationController

static id previousViewControllerAssociatedObjectKey;

- (UIViewController *)previousViewController {
	UIViewController *previousViewController = objc_getAssociatedObject(self, &previousViewControllerAssociatedObjectKey);
	return previousViewController;
}

- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated {
	BOOL delegateConforms = [self.delegate conformsToProtocol:@protocol(PushPopNotifyingNavigationControllerDelegate)];
	UIViewController *previousViewController = self.topViewController;
	
	objc_setAssociatedObject(self, &previousViewControllerAssociatedObjectKey, previousViewController, OBJC_ASSOCIATION_ASSIGN);
	
	if (delegateConforms && [self.delegate respondsToSelector:@selector(navigationController:willPushViewController:)])
		[(id<PushPopNotifyingNavigationControllerDelegate>)self.delegate navigationController:self willPushViewController:viewController];
	if (delegateConforms && [self.delegate respondsToSelector:@selector(navigationController:willPushViewController:onto:)])
		[(id<PushPopNotifyingNavigationControllerDelegate>)self.delegate navigationController:self willPushViewController:viewController onto:previousViewController];
	
	[super pushViewController:viewController animated:animated];
}

- (UIViewController *)popViewControllerAnimated:(BOOL)animated {
	BOOL delegateConforms = [self.delegate conformsToProtocol:@protocol(PushPopNotifyingNavigationControllerDelegate)];
	UIViewController *restoringViewController = (self.viewControllers.count >= 2) ? [self.viewControllers objectAtIndex:self.viewControllers.count - 2] : nil; // one back from the end
	UIViewController *poppedViewController = self.topViewController;
	
	objc_setAssociatedObject(self, &previousViewControllerAssociatedObjectKey, poppedViewController, OBJC_ASSOCIATION_ASSIGN);
	
	if (delegateConforms && [self.delegate respondsToSelector:@selector(navigationController:willPopViewController:)])
		[(id<PushPopNotifyingNavigationControllerDelegate>)self.delegate navigationController:self willPopViewController:poppedViewController];
	if (delegateConforms && [self.delegate respondsToSelector:@selector(navigationController:willPopViewController:backTo:)])
		[(id<PushPopNotifyingNavigationControllerDelegate>)self.delegate navigationController:self willPopViewController:poppedViewController backTo:restoringViewController];
	
	UIViewController *result = [super popViewControllerAnimated:animated];
	
	if (delegateConforms && [self.delegate respondsToSelector:@selector(navigationController:isPoppingViewController:)])
		[(id<PushPopNotifyingNavigationControllerDelegate>)self.delegate navigationController:self isPoppingViewController:poppedViewController];
	if (delegateConforms && [self.delegate respondsToSelector:@selector(navigationController:isPoppingViewController:backTo:)])
		[(id<PushPopNotifyingNavigationControllerDelegate>)self.delegate navigationController:self isPoppingViewController:poppedViewController backTo:restoringViewController];
	
	return result;
}

@end