没有从firebase数据库swift 4中获取数据

Question

我只是想显示用户离该位置有多远，但我似乎无法将任何东西打印到我的控制台上。如果我将代码放在 viewDidLoad 中并手动输入“postLocations”的坐标 我知道了距离，但我似乎无法用我目前的代码打印任何东西。

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    let userLocation: CLLocation = locations[0] as CLLocation

    let ref = Database.database().reference().child("posts")
    ref.observeSingleEvent(of: .value, with: { (snapshot) in

        guard let dictionary = snapshot.value as? [String: AnyObject] else { return }

        guard let latitude = dictionary["latitude"] as? Double else { return }
        guard let longitude = dictionary["longitude"] as? Double else { return }

        let currentLocation = Coordinate(long: userLocation.coordinate.longitude, lat: userLocation.coordinate.latitude)
        let postLocations = Coordinate(long: longitude, lat: latitude)

        if currentLocation.distance(to: postLocations) <= 100 {
            print("You are \(currentLocation.distance(to: postLocations)) away from posts")
        } else {
            print("No posts in area")
        }

    }) { (error) in
        print("There was an error getting posts", error)
    }

    }

Answer 1

在viewDidLoad中试试这段代码，并检查控制台中的打印语句是否打印了经纬度。

func fetchUserLocation() {
     let ref = Database.database().reference().child("posts")
     ref.observeSingleEvent(of: .value, with: { (snapshot) in
     guard let dictionary = snapshot.value as? [String: AnyObject] else { return }
     guard let latitude = dictionary["latitude"] as? String else { return }
     guard let longitude = dictionary["longitude"] as? String else { return }
     print("lat: \(latitude), lon: \(longitude)")
   }) { (error) in
    print("There was an error getting posts", error)
  }
}

Answer 2

您无需在 didUpdateLocations 中调用 Firebase 观察者。 您应该在 viewDidLoad 中调用 Firebase 观察者，以便您可以从 Firebase 数据库中获取用户位置。在观察者观察到用户位置后，您需要获取当前位置，以便您可以比较这 2 个位置。试试这个。

Answer 3

在viewDidLoad() 尝试通过调用以下方式访问 Firebase 数据库：

func getFirebaseUserLocation() {
    let ref = Database.reference(withPath: "posts")
    ref.observe(.value, with: { (snapshot) in
        for child in snapshot.children {
            if let postSnapshots = child as? DataSnapshot  { 
                for postSnapshot in postSnapshots.children {
                    guard let postDictionary = postSnapshot.value as? [String: Any] else { return }
                    guard let latitude = postDictionary["latitude"] as? String, let longitude = postDictionary["longitude"] as? String else { return } 
                    print(latitude, longitude)
                    // here you can access your latitude and longitude as Strings from Firebase Database
                }
            }
        }
    }
}