title: How do I share Firebase auth data across an iOS app?
body: <p>I have an app that has 2 view controllers. One is the login/register page, and the other is the page that SHOULD change a UILabel to say the user's email, but it doesn't. I guess it's because I don't have the data from the first view controller. So how can I get the data from the first view controller?</p>
  
  <p>Here's part of the code from <code>SecondViewController.swift</code></p>
  
  <pre><code>if let user = FIRAuth.auth()?.currentUser {
      self.usernameLabel.text = user.email
      print(user.email)
  }
  </code></pre>