swift

firebase get counter number

    func getLatestCounterNumber() {
        
        
        var int = 0
                ref = Database.database().reference()
        
                ref.observeSingleEvent(of: .value, with: { snapshot in
        
                    if !snapshot.exists() { return }
        
                    //print(snapshot)
        
                    if let userName = snapshot.value!["counter"] as? String {
                        print("asjghdvfashdfsauduhdbvasudfasugdfa")
                        print(userName)
                    }
        
                    // can also use
                    // snapshot.childSnapshotForPath("full_name").value as! String
                })
        
        
        self.ref.child("latest_counter").observeSingleEvent(of: .value, with: { (snapshot) in
            // Get user value
            print(snapshot)
            
            let latest_counter = Int("\(snapshot.value!)")
            int = latest_counter! + 1
            
            self.policy_number = Int64(latest_counter!)
            
            
            self.ref.child("latest_counter").setValue("\(int)") {
                (error:Error?, ref:DatabaseReference) in
                if let error = error {
                    print("Data could not be saved: \(error).")
                } else {
                    print("Data saved successfully!")
                }
            }
            
        }) { (error) in
            print(error.localizedDescription)
        }
        
                    var new_number = 0
                    let db = Firestore.firestore()
                    var counterRef = db.collection("counter")
        
                    //get the last 3 counter number
                    counterRef.order(by: "number", descending: false).limit(to: 1)
        
                    counterRef.getDocuments() { (querySnapshot, err) in
                        if let err = err {
                            print("Error getting documents: \(err)")
                        } else {
                            for document in querySnapshot!.documents {
                                print("COUNTER NUMBER\(document.documentID) => \(document.data())")
                                self.policy_number = document.data()["counter"] as! Int64
                                print("policy number is \(self.policy_number)")
                                new_number  = Int(self.policy_number) + 1
                                print("new number is \(new_number)")
        
        
                                db.collection("counter").addDocument(data: [
                                    "counter": Int(new_number)
                                ]) { err in
                                    if let err = err {
                                        print("Error adding document: \(err)")
                                    } else {
                                        print("counter number generated")
                                    }
                                }
                            }
                        }
                    }
    }