save data code

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let cell = tableView.deque(class: UserCell.self, for: indexPath)
        let uid = Auth.auth().currentUser?.uid
        let ref = Database.database(url: FirebaseHelper.dbURL).reference()
        let key = ref.child("users").childByAutoId().key
        let selectedItem = users[indexPath.row]
        var isFollowing = false
        
        ref.child("users").child(uid!).child("following").queryOrderedByKey().observeSingleEvent(of: .value) { snapshot in
            
            if let following = snapshot.value as? [String : AnyObject] {
                for (ke, value) in following {
                    if value as! String == selectedItem.username {
                        isFollowing = true
                        ref.child("users").child(uid!).child("following/\(ke)").removeValue()
                        ref.child("users").child(selectedItem.userID!).child("followers/\(ke)").removeValue()
                        self.tableView.cellForRow(at: indexPath)?.accessoryType = .none
                    }
                }
            }
            
            if !isFollowing {

                let following = ["following/\(key)" : selectedItem.username]
                let followers = ["followers/\(key)" : selectedItem.username]
                ref.child("users").child(uid!).updateChildValues(following)
                ref.child("users").child(selectedItem.userID!).updateChildValues(followers)
                self.tableView.cellForRow(at: indexPath)?.accessoryType = .checkmark

            }
        }
        ref.removeAllObservers()
    }