Swift Realtime Database からデータの読み込み

座標をDouble型としてRealtime Databaseからの読み込みができません。(読み込んだ値がコンソールでnilと表示されます)エラーもありません。どこが間違っているか教えて下さい。

viewcontroller
1class FirstViewController: UIViewController, CLLocationManagerDelegate {
2
3    @IBOutlet weak var mapView: MKMapView!
4    @IBOutlet weak var latitude: UILabel!
5    @IBOutlet weak var longitude: UILabel!
6    let user = Auth.auth().currentUser?.uid
7    let locationManager = CLLocationManager()
8    var ref: DatabaseReference!
9    var otherUserLatitude: Double? = nil
10    var otherUserLongitude: Double? = nil
11    
12    override func viewDidLoad() {
13        super.viewDidLoad()
14        ref = Database.database().reference()
15        locationManager.delegate = self as! CLLocationManagerDelegate
16    }
17    //上手くいっている
18    @IBAction func userLocation(_ sender: Any)
19    {
20        let refLatitude = ref.child("userLatitude")
21        refLatitude.setValue(latitude.text)
22        let refLongitude = ref.child("userLongitude")
23        refLongitude.setValue(longitude.text)
24        print("位置情報を保存しました")
25    }
26    //DBから取得できていない
27    @IBAction func othersLocation(_ sender: Any)
28    {
29        ref.child("userLatitude").observeSingleEvent(of: .value, with: { (snapshot) in
30        let value = snapshot.value as? NSDictionary
31        let otherUserLatitude = value?["userLatitude"] as? Double
32        //コンソール表示otherUserLatitude: nil
33        print("otherUserLatitude:", otherUserLatitude)
34        }) 
35        ref.child("userLongitude").observeSingleEvent(of: .value, with: { (snapshot) in
36        let value = snapshot.value as? NSDictionary
37        let otherUserLongitude = value?["userLongitude"] as? Double
38        //コンソール表示otherUserLongitude: nil
39        print("otherUserLongitude:", otherUserLongitude)
40        })
41    }
42    func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
43        switch status {
44        case .notDetermined:
45            locationManager.requestWhenInUseAuthorization()
46        case .authorizedWhenInUse:
47            locationManager.startUpdatingLocation()
48        default:
49            break
50        }
51    }
52    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
53        if let coordinate = locations.last?.coordinate {
54            // 現在地を拡大して表示する
55            let span = MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01)
56            let region = MKCoordinateRegion(center: coordinate, span: span)
57            mapView.region = region
58        }
59        guard let newLocation = locations.last else {
60                return
61        }
62        self.latitude.text = "".appendingFormat("%.4f", newLocation.coordinate.latitude)
63        self.longitude.text = "".appendingFormat("%.4f", newLocation.coordinate.longitude)
64        let location = locations.first
65        let latitude = location?.coordinate.latitude
66        let longitude = location?.coordinate.longitude
67        
68        print("latitude: (latitude!)\nlongitude: (longitude!)")
69    }
70
71
72}
73
74