login view controller situation - do I need a custom delegate?

AppDelegate.m

// 1. App starts
// 2. If user is not logged in, rootViewController presents loginViewController (Code below)
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
  ...
  //    Now check for authentication
  [self checkIfLoggedIn];
  ...
  return YES;
}

...

- (void)checkIfLoggedIn {
    NSString *authToken = [SSKeychain passwordForService:@"FinalCard-AuthClient" account:@"auth_token"];
    if (authToken != nil) {
        NSLog(@"Have a user with auth_token: %@", authToken);
        FCLoginViewController *fvc =[[FCLoginViewController alloc] init];
        [self.viewController.frontViewController presentViewController:fvc animated:YES completion:nil];
    }
}

// 3. User logs in
// 4. loginViewController is unshown, and user returns to rootViewController

// QUESTION: 
// How do I notify rootViewController that the user has logged in and then remove loginViewController?