title: Swift & FirebaseIO query filtering not finding child
body: <p>My app uses a barcode scanner (1D-3D) to get a code/tag, then validate it against my FirebaseIO and return as valid/invalid if found/not found. 
  The scanning works and console can print the tag nr everytime, although I cant figure out how to find that nr back in the Firebase?</p>
  
  <pre><code>self.tapHandler = { point in            print(point)                    self.barcodesHandler = { barcodes in                for barcode in barcodes {                    print(barcode.stringValue ?? "")                    let tags = barcode.stringValue                                        let query = dbref.queryOrdered(byChild: "Tag").queryEqual(toValue: tags)                    query.observe(.value, with: { (snapshot) in                for childSnapshot in snapshot.children {                    print("tag is ")                    print(childSnapshot)                }            })
  </code></pre>
  
  <p>and my firebase structure (where Tag is the lookup field)
  '''</p>
  
  <pre><code>{
    "members" : {
      "4b4ac23c9f184ce8b31fde011cd3a696" : {
        "Tag" : 82644,
        "Title" : "Mr",
        "Uid" : 80,
        "Username" : "orange"
      },
  </code></pre>