UIViewController default back button action

UIViewController+BackButtonHandler.h

#import <UIKit/UIKit.h>

@protocol BackButtonHandlerProtocol <NSObject>

@optional

-(BOOL)navigationShouldPopOnBackButton;

@end

@interface UIViewController (BackButtonHandler) <BackButtonHandlerProtocol>

@end

UIViewController+BackButtonHandler.m

#import "UIViewController+BackButtonHandler.h"

@implementation UIViewController (BackButtonHandler)

@end

@implementation UINavigationController (ShouldPopOnBackButton)

- (BOOL)navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item {

if([self.viewControllers count] < [navigationBar.items count]) {

return YES;

}

BOOL shouldPop = YES;

UIViewController* vc = [self topViewController];

if([vc respondsToSelector:@selector(navigationShouldPopOnBackButton)]) {

shouldPop = [vc navigationShouldPopOnBackButton];

}

if(shouldPop) {

dispatch_async(dispatch_get_main_queue(), ^{

[self popViewControllerAnimated:YES];

});

} else {

for(UIView *subview in [navigationBar subviews]) {

if(subview.alpha < 1.) {

[UIView animateWithDuration:.25 animations:^{

subview.alpha = 1.;

}];

}

}

}

return NO;

}

@end

put this code in your child view controller 

#import "UIViewController+BackButtonHandler.h"

-(BOOL) navigationShouldPopOnBackButton

{

[[[UIAlertView alloc] initWithTitle:@"Confirmation" message:@"Are you sure you want to go back?"

  delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes", nil] show];

return NO;

}

- (void)alertView:(UIAlertView *)alertView willDismissWithButtonIndex:(NSInteger)buttonIndex

{

if(buttonIndex==1) {

[self.navigationController popViewControllerAnimated:YES];

}

}