instagram like

  func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        
        let uid = FIRAuth.auth()!.currentUser!.uid
        let ref = FIRDatabase.database().reference()
        let key = ref.child("users").childByAutoId().key
        
        var isFollower = false
        
        ref.child("users").child(uid).child("following").queryOrderedByKey().observeSingleEvent(of: .value, with: { snapshot in
        
            if let following = snapshot.value as? [String : AnyObject] {
                for (ke, value) in following {
                    if value as! String == self.user[indexPath.row].userID {
                        isFollower = true
                        
                        ref.child("users").child(uid).child("following/\(ke)").removeValue()
                        ref.child("users").child(self.user[indexPath.row].userID).child("followers/\(ke)").removeValue()
                        
                        self.tableview.cellForRow(at: indexPath)?.accessoryType = .none
                    }
                }
            }
            if !isFollower {
                let following = ["following/\(key)" : self.user[indexPath.row].userID]
                let followers = ["followers/\(key)" : uid]
                
                ref.child("users").child(uid).updateChildValues(following)
                ref.child("users").child(self.user[indexPath.row].userID).updateChildValues(followers)
                
                self.tableview.cellForRow(at: indexPath)?.accessoryType = .checkmark
            }
        })
        ref.removeAllObservers()
        
    }
    
    
    func checkFollowing(indexPath: IndexPath) {
        let uid = FIRAuth.auth()!.currentUser!.uid
        let ref = FIRDatabase.database().reference()
        
        ref.child("users").child(uid).child("following").queryOrderedByKey().observeSingleEvent(of: .value, with: { snapshot in
            
            if let following = snapshot.value as? [String : AnyObject] {
                for (_, value) in following {
                    if value as! String == self.user[indexPath.row].userID {
                        self.tableview.cellForRow(at: indexPath)?.accessoryType = .checkmark
                    }
                }
            }
        })
        ref.removeAllObservers()
        
    }