title: Finding an UID by email in Firebase
body: <p>I first attempted to instantiate each user in the database like so:</p>
  
  <pre><code>emails : {
      email: "jerry@gmail.com" {
          uid: "x"
      }
  }
  </code></pre>
  
  <p>I quickly found out that I can't store an email because it has an <code>@</code> and <code>.</code>. I was originally going to do an user look up like so:</p>
  
  <pre><code>func userLookUpByEmail (email: String) -&gt; String {
      var userID: String = "nil"
  
      ref.queryOrderedByChild("emails").queryEqualToValue(email).observeSingleEventOfType(.ChildAdded, withBlock: { snapshot in
              if snapshot.value != nil {
                  print(snapshot.value)
                  userID = snapshot.value as! String
              }
              else {
                  print ("user not found")
                  userID = "nil"
              }
      })
      return userID
  }
  </code></pre>
  
  <p>However, I'm realizing that won't work. What is an effective way to receive an UID from providing an email?</p>