gistfile1.m

- (BOOL)navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item {
	// ...
	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;
}