UINavigationController UINavigationControllerHideShowBarDuration example in Objective C (iOS).

UINavigationController UINavigationControllerHideShowBarDuration

A global variable that specifies a preferred duration when animating the navigation bar.

extern const CGFloat UINavigationControllerHideShowBarDuration
Constants
UINavigationControllerHideShowBarDuration
This variable specifies the duration when animating the navigation bar. Note that this is a constant value, so it cannot be set.

UINavigationController UINavigationControllerHideShowBarDuration example.

[self.navigationController setNavigationBarHidden:YES animated:YES];
 [UIView transitionWithView:self.view
                   duration:UINavigationControllerHideShowBarDuration
                    options:UIViewAnimationOptionCurveLinear
                 animations:^
  {
   /* Put other animation code here ;) */
  }
                 completion:^(BOOL finished)
  {                                 
  }];

Example of [UINavigationController UINavigationControllerHideShowBarDuration].

- (void)pushViewControllerAfterAnimation:(UIViewController *)viewController animated:(BOOL)animated {
    [UIView transitionWithView:viewController.view
                      duration:UINavigationControllerHideShowBarDuration
                       options:UIViewAnimationCurveEaseOut
                    animations:^{
                        [self.navigationController setNavigationBarHidden:NO];    
                    }
                    completion:^(BOOL finished){
                        NSLog(@"animation finished");
                        [self pushViewController:viewController animated:animated];
                    }];
}

- (void)popViewControllerAfterAnimationAnimated:(BOOL)animated {
    [UIView transitionWithView:self.visibleViewController.view
                      duration:UINavigationControllerHideShowBarDuration
                       options:UIViewAnimationCurveEaseOut
                    animations:^{
                        [self.navigationController setNavigationBarHidden:YES];    
                    }
                    completion:^(BOOL finished){
                        NSLog(@"animation finished");
                        [self popViewControllerAnimated:animated];
                    }];
}

UINavigationController UINavigationControllerHideShowBarDuration example.

Only improvement would be setting anim duration to be consistent with other navigation controller animations:

    [UIView setAnimationDuration:UINavigationControllerHideShowBarDuration];

End of UINavigationController UINavigationControllerHideShowBarDuration example article.