Firebase removeObserver is not working in Swift 5

I am using Firebase's Realtime database in my app. I am fetching data from the database and do some change and after that I am removing the observer which is not working fine.

I have some data in Realtime Database like this:

I am using firebase's observe(.value) function to get this value and after that I am updating an entry and then I am removing the observer. This is my code:

func updatePoints() {
        
        let firebaseId = UserDefaults.standard.value(forKey: "firebaseId") as? String ?? ""
        
        let reference = self.database.child("Points").child(firebaseId)
        var handler : UInt = 0
        
        handler = reference.observe(.value, with: { snapshot in
            
            guard let userPoints = snapshot.value as? [String : Any] else {
                print("no points data found")
                return
            }
            

            let pointsLeft = userPoints["points_left"] as? Int ?? 0
            
            reference.child("points_left").setValue(pointsLeft - 1)

            reference.removeObserver(withHandle: handler)
        })
    }

The problem now is, this observer runs twice. For example, if "points_left" : 10, then after this function the points left will have 8 value but it should have 9 instead. It is running twice and I am not understanding why is it doing so as I am using removeObserver. Can someone help me with this?

The reason to the above unexpected behaviour is the setValue function you called to update the points is triggering another .value event in the database. Then it triggers the observer again. Therefore, by the time you remove the observer, it has already triggered twice. This leads to decrease of points by 2 instead of 1.

So if u interchange the last two lines, by the time you call the setValue function observer is removed. So it will not get triggered for the second time.