Ios 同时从TableView和Firebase中删除行

我试图使用单元格上的delete按钮删除firebase数据库中的条目，我可以从数据库中删除它，但它仍保留在表视图中，我不知道如何将应用程序延迟到firebase更新数据库之后，以便正确重新加载表数据

var contacts = [Contact]()

override func viewDidLoad() {
    contactsTable.delegate = self
    contactsTable.dataSource = self
    super.viewDidLoad()
    fetchContacts(){
        self.contactsTable.reloadData()
    }
}
func fetchContacts(completion: @escaping () -> ()){
    contacts = [Contact]()
    let userRef = FIRDatabase.database().reference()

    userRef.observe(.childAdded, with: { (snapshot) in
        print(snapshot)
        if let dictionary = snapshot.value as? [String: AnyObject]{
            let contact = Contact()
            contact.setValuesForKeys(dictionary)
            self.contacts.append(contact)
        }
        completion()
    }, withCancel: nil)

}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell:ContactCell = self.contactsTable.dequeueReusableCell(withIdentifier: "contactCell") as! ContactCell

        cell.tapTrashAction = { [weak self] (cell) in
        let alert = UIAlertController(title: "Confirm", message: "Are you sure you want to delete \(contactName!) as a contact?", preferredStyle: UIAlertControllerStyle.alert)

        alert.addAction(UIAlertAction(title: "Delete", style: UIAlertActionStyle.destructive, handler:{ action in
        self!.handleDelete(phone: phoneNumber!)
        //self?.contactsTable.deleteRows(at: [indexPath], with: UITableViewRowAnimation.fade)
        }))
        alert.addAction(UIAlertAction(title: "Cancel", style: UIAlertActionStyle.cancel, handler: nil))

        self?.present(alert, animated: true, completion: nil)

    }
    return cell
}
func handleDelete(phone: String){
    let userRef = FIRDatabase.database().reference()
    userRef.child(phone).removeValue { (error, ref) in
        if error != nil {
            print("Error: \(error)")
        }
        self.fetchContacts(){
            self.contactsTable.reloadData()
        }
    }
}

---

当前代码只观察

.childAdded

事件，这意味着它只处理添加新子节点时的情况

要在删除子节点时处理，还需要观察并处理

.childRemoved

事件：

userRef.observe(.childRemoved, with: { (snapshot) in
    // TODO: remove user from self.contacts and update table view

---

当前代码只观察

.childAdded

事件，这意味着它只处理添加新子节点时的情况

要在删除子节点时处理，还需要观察并处理

.childRemoved

事件：

userRef.observe(.childRemoved, with: { (snapshot) in
    // TODO: remove user from self.contacts and update table view