title: Checking if Firebase snapshot is equal to nil in Swift
body: <p>I am trying to query Firebase to check if any user that has <code>waiting: "1"</code> and then when the snapshot is returned I want to see whether it is equal to nil. I have attempted to do this but the method I have used does not work and I only have some sort of out put if the snapshot is not equal to nil. I have added the code I currently have and the JSON text from Firebase.</p>
  
  <pre><code>import UIKit
  import Firebase
  import Spring
  
  class GamesViewController: UIViewController {
  
  let ref = Firebase(url: "https://123test123.firebaseio.com")
  var activityIndicator: UIActivityIndicatorView = UIActivityIndicatorView()   
  
  @IBAction func StartGamePressed(sender: AnyObject) {
      print("test1")
      var peopleWaiting: [String] = []
  
      let userRef = Firebase(url:"https://123test123.firebaseio.com/users")
      userRef.queryOrderedByChild("waiting").queryEqualToValue("1")
          .observeEventType(.ChildAdded, withBlock: { snapshot in
              print(snapshot.key)
              if snapshot.key == nil {
                  print("test2")
                  let userData = ["waiting": "1"]
                  let usersRef = self.ref.childByAppendingPath("users")
                  let hopperRef = usersRef.childByAppendingPath("\(self.ref.authData.uid)")
  
                  hopperRef.updateChildValues(userData, withCompletionBlock: {
                      (error:NSError?, ref:Firebase!) in
                      if (error != nil) {
                          print("Data could not be saved.")
                          self.displayAlert("Oops!", message: "We have been unable to get you into a game, check you have an internet conection. If this problem carries on contect support")
                      } else {
                          print("Data saved successfully!")
                          let storyboard = UIStoryboard(name: "Main", bundle: nil)
                          let Home : UIViewController = storyboard.instantiateViewControllerWithIdentifier("continueToGame")
                          self.presentViewController(Home, animated: true, completion: nil)
  
                      }
  
                  })
  
  
              } else {
                  var randomUID: String
                  peopleWaiting.append(snapshot.key)
                  let randomIndex = Int(arc4random_uniform(UInt32(peopleWaiting.count)))
                  randomUID = peopleWaiting[randomIndex]
                  print(randomUID)
                  let storyboard = UIStoryboard(name: "Main", bundle: nil)
                  let Home : UIViewController = storyboard.instantiateViewControllerWithIdentifier("continueToGame")
                  self.presentViewController(Home, animated: true, completion: nil)
  
              }
          })
  }
  
  func displayAlert(title: String, message: String){
  
      let formEmpty = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.Alert)
      formEmpty.addAction((UIAlertAction(title: "Ok", style: .Default, handler: { (action) -&gt; Void in
  
      })))
  
      self.presentViewController(formEmpty, animated: true, completion: nil)
  }
  
  func activityIndicatorFunction(){
  
      activityIndicator = UIActivityIndicatorView(frame: CGRectMake(0, 0, 100, 100))
      activityIndicator.backgroundColor = UIColor(red:0.16, green:0.17, blue:0.21, alpha:1)
      activityIndicator.layer.cornerRadius = 6
      activityIndicator.center = self.view.center
      activityIndicator.hidesWhenStopped = true
      activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.WhiteLarge
      view.addSubview(activityIndicator)
      activityIndicator.startAnimating()
      UIApplication.sharedApplication().beginIgnoringInteractionEvents()
  
  }
  
  
  }
  </code></pre>
  
  <p>JSON Data:</p>
  
  <pre><code>{
  "68e42b7f-aea5-4c3f-b655-51a99cb05bb0" : {
    "email" : "test1@test1.com",
    "username" : "test1",
    "waiting" : "0"
  },
  "8503d5a8-fc4a-492b-9883-ec3664898b4f" : {
    "email" : "test2@test2.com",
    "username" : "test2",
    "waiting" : "0"
  }
  }
  </code></pre>