title: Can't get number of children from a snapshot
body: <p>I can't get the number of children returned by snapshot. I always get <code>Snap ((null)) (null)</code> when I write <code>print(self.newCars)</code> in another position:</p>
  
  <pre><code>class NewCarsViewController: UICollectionViewController {
      var firebase: FIRDatabaseReference?
  
      var newCars = FIRDataSnapshot()
  
      override func viewDidLoad() {
          super.viewDidLoad()
  
          self.firebase = FIRDatabase.database().reference(fromURL:"https://firebaseURL/").child("featuredCars")
          firebase?.observeSingleEvent(of: .value, with: { snapshot in
              self.newCars = snapshot
              print("halim")
              print(self.newCars)
              //  print(snapshot.childrenCount) // I got the expected number of items
              for rest in snapshot.children.allObjects as! [FIRDataSnapshot] {
                 //   print(rest.value ?? "")
              }
          })
  
      }
  
      override func numberOfSections(in collectionView: UICollectionView) -&gt; Int {
          return 1
      }
      override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -&gt; Int {
  
          return 1
      }
      override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -&gt; UICollectionViewCell {
          let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "NewCarCell", for: indexPath) as UICollectionViewCell
          return cell
              }
  
  }
  </code></pre>