Subclass of UINavigationController which keeps the view controller outgoing over push/pop for UINavigationControllerDeletgate's navigationController:willShowViewController:animated:. The view controller can be referenced like `navigationController.outgoingViewController`.

A2NavigationController.h

#import <UIKit/UIKit.h>

@interface A2NavigationController : UINavigationController
{
    UIViewController *_outgoingViewController;
}

- (UIViewController *)outgoingViewController;

@end

A2NavigationController.m

#import " A2NavigationController.h"

@implementation  A2NavigationController

- (id)initWithRootViewController:(UIViewController *)rootViewController
{
    self = [super initWithRootViewController:rootViewController];
    if (self) {
        _outgoingViewController = nil;
    }
    return self;
}

- (UIViewController *)outgoingViewController
{
    return _outgoingViewController;
}

- (NSArray *)popToRootViewControllerAnimated:(BOOL)animated
{
    _outgoingViewController = self.visibleViewController;
    NSArray *ret = [super popToRootViewControllerAnimated:animated];
    _outgoingViewController = nil;
    return ret;
}

- (NSArray *)popToViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    _outgoingViewController = self.visibleViewController;
    NSArray *ret = [super popToViewController:viewController animated:animated];
    _outgoingViewController = nil;
    return ret;
}

- (UIViewController *)popViewControllerAnimated:(BOOL)animated
{
    _outgoingViewController = self.visibleViewController;
    UIViewController *ret = [super popViewControllerAnimated:(BOOL)animated];
    _outgoingViewController = nil;
    return ret;
}

- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    _outgoingViewController = self.visibleViewController;
    [super pushViewController:viewController animated:animated];
    _outgoingViewController = nil;
}

@end