Type conversion error when reading data from Firebase

Question

I'am using mapkit to make a app, while I trying to get the user location from firebase it cause the error in these three line

let dict = recipeSnap.value as! [String:Double?]

let latitude = dict["latitude"] as? Double?

let longitude = dict["longitude"] as? Double?.

I have tried to replace the double by string but new error happen, then I tried replace it by AnyObject, it works, but the data is like Optional(37.785834). and it always cause the error while I use AnyObject data to do other things.

here is my code

@objc func updateTimer(){

    print("Update location")
    let location = locman.location!.coordinate
    lat = String(location.latitude)
    long = String(location.longitude)
    print(lat)
    print(long)
    let ref = Database.database().reference()
    ref.child("location/User1/longitude").setValue(long)
    ref.child("location/User1/latitude").setValue(lat)
    ref.child("location").observeSingleEvent(of: .value) { (snapshot) in
          self.usern = snapshot.childrenCount
          for snap in snapshot.children{
              let aSnap = snap as! DataSnapshot  
              let dict = aSnap.value as! [String:Double?]
              let latitude = dict["latitude"] as? Double?
              let longitude = dict["longitude"] as? Double?
              print(dict)
              print(latitude)
              print(longitude)

              let point = MKPointAnnotation()
              point.title = "user"
            //point.coordinate = CLLocationCoordinate2D(latitude: CLLocationDegrees(latitude), longitude: CLLocationDegrees(longitude))
              self.mapView.addAnnotation(point)
        }
    }
}

and here is my error

Could not cast value of type 'Swift._NSContiguousString' (0x1032681f8) to 'NSNumber' (0x1b7a1abf0). 2019-10-10 20:24:05. mapkitMap[1468:709956] Could not cast value of type 'Swift._NSContiguousString' (0x1032681f8) to 'NSNumber' (0x1b7a1abf0). Optional(37.785834)

while I try to replace Double by string a new error appear

Could not cast value of type '__NSCFNumber' (0x1b7a0e0e0) to 'NSString' (0x1b7a1aad8). 2019-10-10 20:20:32.1 mapkitMap[1465:708355] Could not cast value of type '__NSCFNumber' (0x1b7a0e0e0) to 'NSString' (0x1b7a1aad8).

I wrote a quick answer below, but then realized that you seem to have a mix of strings and doubles in your database. Can you update your question to include the JSON that is causing the problem (as text, no screenshot please)? You can get this by clicking the "Export JSON" link in the overflow menu (⠇) on your Firebase Database console. — Frank van Puffelen

Frank van Puffelen Frank van Puffelen · Accepted Answer · 2019-10-10T13:07:16

You seem to be storing some of your latitude and longitude as string values,

lat = String(location.latitude)
long = String(location.longitude)

so you can't simply retrieve them from the database as numbers. You'll need to read them from the database as strings, and then parse their numeric value.

Something like:

  let aSnap = snap as! DataSnapshot  
  let latitude = Double(snap.childSnapshot(forPath: "latitude").value)
  let longitude =  Double(snap.childSnapshot(forPath: "longitude").value)

Type conversion error when reading data from Firebase

1 Answers