title: Present a View before Tab Bar Controller
body: <p>I'm developing an app that will use a tab bar controller. But before this tab bar controller appear I need to authenticate the user. So I'm trying to load a View before the Tab bar controller appear.
  Here is what I did so far:
  I'm using a Tabbed Application, and in the storyboard is the tab bar controller.
  I created a View Controller called LoginViewController, which contains it's own xib.</p>
  
  <p>So in the <strong>AppDelegate</strong> didFinishLaunchingWithOptions: method I did this:</p>
  
  <pre><code>LoginViewController *loginViewController = [[LoginViewController alloc] initWithNibName:@"LoginViewController" bundle:NULL];
  self.window.rootViewController = loginViewController;
  [self.window addSubview:loginViewController.view];
  </code></pre>
  
  <p>Then, in the <strong>LoginViewController</strong> implementation I created a method that will be called when the login is successful. Here is how it looks like:</p>
  
  <pre><code>- (void)removeLoginView
  {
  AppDelegate *delegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
  [delegate removeLoginView];
  }
  </code></pre>
  
  <p>Now I don't know how I should implement this method in the AppDelegate.
  How could I remove the loginViewController and set the TabBar controller from the storyboard to be shown? Or any other suggestions on how to do something like this.</p>
  
  <p>Note: I saw some suggestions about using presentModalViewController, but it has been deprecated.</p>