title: How to change the present view controller?
body: <p>I have a login view controller which make a request to the server for authentification.  Once it is success, I want the present view controller to be the home tab view controller of my application.  I did try to use pushViewController:viewController or presentModalViewController or dismissModalViewControllerAnimated.  Nothing works.  You can take a look at the screenshot provided to understand my application flow.</p>
  
  <p>Here is some sample code:</p>
  
  <pre><code>- (IBAction)facebookLoginButtonClick:(id)sender {
  
  // get the app delegate so that we can access the session property
  AppDelegate *appDelegate = [[UIApplication sharedApplication]delegate];
  
  // this button's job is to flip-flop the session from open to closed
  if (appDelegate.session.isOpen) {
      // if a user logs out explicitly, we delete any cached token information, and next
      // time they run the applicaiton they will be presented with log in UX again; most
      // users will simply close the app or switch away, without logging out; this will
      // cause the implicit cached-token login to occur on next launch of the application
      [appDelegate.session closeAndClearTokenInformation];
  
  } else {
      if (appDelegate.session.state != FBSessionStateCreated) {
          // Create a new, logged out session.
          appDelegate.session = [[FBSession alloc] init];
      }
  
      // if the session isn't open, let's open it now and present the login UX to the user
      [appDelegate.session openWithCompletionHandler:^(FBSession *session,
                                                       FBSessionState status,
                                                       NSError *error) {
          // and here we make sure to update our UX according to the new session state
          [self dismissModalViewControllerAnimated:YES];
          UIStoryboard *mainStoryboard = [UIStoryboard storyboardWithName:@"MainStoryboard_iPhone" bundle: nil];
          MainViewTabBarController *viewController = (MainViewTabBarController*)[mainStoryboard instantiateViewControllerWithIdentifier: @"mainPageTabBarId"];
          [[self navigationController] presentModalViewController:viewController animated:YES];
      }];
  }
  </code></pre>
  
  <p>}</p>
  
  <p><img src="https://i.stack.imgur.com/e3nAm.png" alt="enter image description here"></p>