Firebase/iOS:runTransactions有时不起作用

Question

我正在开发一个聊天应用程序,用户应该收到有关其联系人新消息的通知.此通知消息还应包括未读消息的数量.因为发送方和接收方都可以更新此信息runTransaction是首选.不幸的是,有时它不起作用.感觉"卡住",然后再一次开始工作.该privateChats节点(见下文)被始终与最新的消息更新,而不是openChatMessages节点.

如果在很短的时间内发送了许多消息,即runTransactions对于同一个消息执行得太频繁,会发生这种情况ref吗？

我的数据结构:

privateChats
    $userId
        $chatId
            $messageId
                text
                timestamp
                senderId
                senderEmail
                senderName

// this node contains information about open chats
// like last message and counter for unread messages
openChatMessages
    $userId
        $chatId
            text
            timestamp
            senderId
            senderEmail
            senderName
            counter

我的代码:

class ChatViewController: JSQMessagesViewController {

    var user: FIRUser!
    var ref: FIRDatabaseReference!
    var chatRef: FIRDatabaseReference!
    var senderOpenChatRef: FIRDatabaseReference!
    var receiverOpenChatRef: FIRDatabaseReference!

    // the following variables will be set before ChatViewController appears

    var chatId: String?
    var receivId: String?
    var receiverEmail: String?
    var receiverName: String?

    override func viewDidLoad() {
        super.viewDidLoad()
        self.user = FIRAuth.auth()?.currentUser!
        self.ref = FIRDatabase.database().reference()
        self.chatRef = self.ref.child("privateChats").child(self.user.uid).child(self.chatId!)
        self.senderOpenChatRef = self.ref.child("openChatMessages").child(self.user.uid).child(self.chatId!)
        self.receiverOpenChatRef = self.ref.child("openChatMessages").child(self.receiverId!).child(self.chatId!)
    }

    func sendMessage(text: String) {
        var messageObject = [String: AnyObject]()
        messageObject["text"] = text
        messageObject["timestamp"] = FIRServerValue.timestamp()
        messageObject["senderEmail"] = self.user.email
        messageObject["senderName"] = self.user.displayName
        messageObject["senderId"] = self.user.uid

        let messageId = self.ref.child("privateChats").child(self.user.uid).child(self.chatId!).childByAutoId().key

        let childUpdates = [
            "/privateChats/\(self.user.uid)/\(self.chatId!)/\(messageId)": messageObject,
            "/privateChats/\(self.receiverId!)/\(self.chatId!)/\(messageId)": messageObject
        ]

        self.ref.updateChildValues(childUpdates, withCompletionBlock: { (error, ref) -> Void in
            if error != nil {
                print("childUpdates error:\(error)")
                return
            }

            JSQSystemSoundPlayer.jsq_playMessageSentSound()
            self.finishSendingMessage()
            self.updateOpenChats(text)
        })
    }


    func updateOpenChats(text: String) {

        // update the receivers openChatObject with increasing the counter
        self.receiverOpenChatRef.runTransactionBlock({ (currentData: FIRMutableData) -> FIRTransactionResult in

            var openChatObject = [String: AnyObject]()

            // update openChatObject with the latest information from currentData
            if currentData.hasChildren() {
                 openChatObject = currentData.value as! [String: AnyObject]
            }

            openChatObject["text"] = text
            openChatObject["timestamp"] = FIRServerValue.timestamp()
            openChatObject["senderEmail"] = self.user.email
            openChatObject["senderName"] = self.user.displayName
            openChatObject["senderId"] = self.user.uid

            var counter = openChatObject["counter"] as? Int
            if counter == nil {
                counter = 1
            } else {
                counter = counter! + 1
            }
            openChatObject["counter"] = counter

            currentData.value = openChatObject
            return FIRTransactionResult.successWithValue(currentData)
            }) { (error, committed, snapshot) in
                if let error = error {
                    print("updateOpenChats: \(error.localizedDescription)")
                }
        }

        // update your (the sender's) openChatObject with setting the counter to zero
        self.senderOpenChatRef.runTransactionBlock({ (currentData: FIRMutableData) -> FIRTransactionResult in

            var openChatObject = [String: AnyObject]()

            // update openChatObject with the latest information from currentData
            if currentData.hasChildren() {
                 openChatObject = currentData.value as! [String: AnyObject]
            }

            openChatObject["text"] = text
            openChatObject["timestamp"] = FIRServerValue.timestamp()
            openChatObject["senderEmail"] = self.receiverEmail
            openChatObject["senderName"] = self.receiverName
            openChatObject["senderId"] = self.receiverId
            openChatObject["counter"] = 0

            currentData.value = openChatObject
            return FIRTransactionResult.successWithValue(currentData)
            }) { (error, committed, snapshot) in
                if let error = error {
                    print(error.localizedDescription)
                }
        }
    }
}

编辑:

与我的第一个答案的期望相反,错误仍然存​​在.我认为它与连接有关？例如,当没有良好的连接时,有时需要更长的时间来运行交易？但有时当我坐在路由器旁边时也会发生这种情况.其他节点被写入,但不会写入事务.在这些情况下重新启动应用程序后,它再次开始工作.所以我觉得引擎盖下有什么问题.

我非常感谢这个问题的解决方案.接收器有时不会收到有关新消息的通知的聊天应用程序是不行的.

我也可以使用变通方法:当你想增加一个计数器时,实际上是否需要交易？我可以更新其他数据一样text,senderId或者timestamp有setValue,但会导致数据损坏,当两个用户试图在同一时间设置子节点的值,不是吗？

这是我的最新代码:

func sendMessage(text: String?, video: NSURL?, image: UIImage?) {

    var messageObject = [String: AnyObject]()
    messageObject["text"] = text
    messageObject["timestamp"] = FIRServerValue.timestamp()
    messageObject["senderEmail"] = self.user.email
    messageObject["senderName"] = self.user.displayName
    messageObject["senderId"] = self.user.uid

    func completeSending() {
        let messagesRef = self.ref.child("messages").child(self.chatId!).childByAutoId()
        messagesRef.setValue(messageObject)

        JSQSystemSoundPlayer.jsq_playMessageSentSound()
        if let _ = image {
            self.updateOpenChats(" Photo")
        } else if let text = text {
            self.updateOpenChats(text)
        }

        self.finishSendingMessageAnimated(true)
    }

    if let image = image { // if an image is being sent
        let data: NSData = UIImageJPEGRepresentation(image, 0.37)!
        let fileName = "image_\(NSDate().timeIntervalSince1970).jpg"
        let chatImagesRef = storageRef.child("chatImages/\(self.chatId!)/\(fileName)")
        let uploadTask = chatImagesRef.putData(data, metadata: nil) { metadata, error in
            if (error != nil) {
                print(error)
                return
            }
        }

        uploadTask.observeStatus(.Failure) { snapshot in
            ProgressHUD.showError("Uploading image failed.")
        }

        uploadTask.observeStatus(.Success) { snapshot in
            let imageUrl = snapshot.reference
            messageObject["imageUrl"] = String(imageUrl)
            completeSending()
        }
    } else { // if it's just a text message
        completeSending()
    }

}

func updateOpenChats(text: String) {

        self.receiverChatRef.runTransactionBlock({ (currentData: FIRMutableData) -> FIRTransactionResult in

            var openChatObject = [String: AnyObject]()

            if currentData.hasChildren() {
                openChatObject = currentData.value as! [String: AnyObject]
            }

            openChatObject["text"] = text
            openChatObject["timestamp"] = FIRServerValue.timestamp()
            openChatObject["senderEmail"] = self.user.email
            openChatObject["senderName"] = self.user.displayName
            openChatObject["senderId"] = self.user.uid
            openChatObject["pushId"] = Database.pushId

            var counter = openChatObject["counter"] as? Int
            if counter == nil {
                counter = 1
            } else {
                counter = counter! + 1
            }
            openChatObject["counter"] = counter

            // Set value and report transaction success
            currentData.value = openChatObject
            return FIRTransactionResult.successWithValue(currentData)
        }) { (error, committed, snapshot) in
            if let error = error {
                print("updateOpenChats: \(error.localizedDescription)")
            }
        }

        self.senderChatRef.runTransactionBlock({ (currentData: FIRMutableData) -> FIRTransactionResult in
            var openChatObject = [String: AnyObject]()

            if currentData.hasChildren() {
                openChatObject = currentData.value as! [String: AnyObject]
            }

            openChatObject["text"] = text
            openChatObject["timestamp"] = FIRServerValue.timestamp()
            openChatObject["senderEmail"] = self.receiver.email
            openChatObject["senderName"] = self.receiver.name
            openChatObject["senderId"] = self.receiver.uid
            openChatObject["counter"] = 0

            // Set value and report transaction success
            currentData.value = openChatObject
            return FIRTransactionResult.successWithValue(currentData)
        }) { (error, committed, snapshot) in
            if let error = error {
                print(error.localizedDescription)
            }
    }
}

Answer 1

好吧，显然 Firebase SDK 中有一个错误。updateChildValues即使更新成功，有时也不会执行回调。我删除了completionBlock，现在它可以完美地工作。

  self.ref.updateChildValues(childUpdates) 
  JSQSystemSoundPlayer.jsq_playMessageSentSound()
  self.finishSendingMessage()
  self.updateOpenChats(text)

编辑： 查看更新的问题，问题仍然出现。