我想在 authenticationViewController 之后更改 rootViewController 
 
-(IBAction)LoginButtonPushed:(id)sender {
    if ([(VerifyId)isEqual:@"C"]){
        CondidatsViewController *condidatsViewController = [[[CondidatsViewController alloc]initWithNibName:@"CondidatsViewController" bundle:nil]autorelease];
        UINavigationController *navController = self.navigationController;
        NSMutableArray *controllers = [[self.navigationController.viewControllers mutableCopy] autorelease];
        [controllers removeLastObject];
        navController.viewControllers = controllers;
        [navController pushViewController:condidatsViewController animated: YES];
    } else {
        RecruteursViewController *recruteursViewController = [[[RecruteursViewController alloc]initWithNibName:@"RecruteursViewController" bundle:nil]autorelease];
        UINavigationController *navController = self.navigationController;
        NSMutableArray *controllers = [[self.navigationController.viewControllers mutableCopy] autorelease];
        [controllers removeLastObject];
        navController.viewControllers = controllers;
        [navController pushViewController:recruteursViewController animated: YES];
    }
}
此代码是当我按下登录按钮时,我希望 CondidatsViewController 或 RecruteursViewController 将成为 rootView
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
    // Override point for customization after application launch.
    AcceuilViewController *viewController =[[[AcceuilViewController alloc]
                                             initWithNibName:@"AcceuilViewController" bundle:nil]autorelease];
    self.navController = [[[UINavigationController alloc]initWithRootViewController:viewController]
                         autorelease];
   self.window.rootViewController = self.navController;
    [self.window makeKeyAndVisible];
    return YES;
}