set this in your first UIViewController inside a NavigationController if you don't want the top bar on the first screen (which is our case on MobileGoplan)

gistfile1.mm

// makes navigation bar disappear when this view about to come on
- (void) viewWillAppear:(BOOL)animated
{
    [self.navigationController setNavigationBarHidden:YES animated:animated];
    [super viewWillAppear:animated];
}

// makes navigation bar appear when this view is about to go away
- (void) viewWillDisappear:(BOOL)animated
{
    [self.navigationController setNavigationBarHidden:NO animated:animated];
    [super viewWillDisappear:animated];
}