Real-Time Counter Distribution Firebase Mismatch

Question

I have a fast iOS application using a real-time Firebase database. If I usually use the application, I still can not find any problems. However, I want to expect extreme cases.

I am trying to emphasize a test application before I click update, and one of the ways I do it is quickly moving from VC using tableView to the next VC, which is a detailed VC. If I do this several times, the table view will show a lot of duplicate data.

I tested my application by opening a table view on my simulator and going to my Firebase Console and manually changing the value, and the line instantly changed on the device.

Therefore, I am confused why in my table view the wrong number of children is displayed if it constantly checks what value should be.

// MARK: Firebase Methods func checkIfDataExits() { DispatchQueue.main.async { self.cardArray.removeAll() self.ref.observe(DataEventType.value, with: { (snapshot) in if snapshot.hasChild("cards") { self.pullAllUsersCards() } else { self.tableView.reloadData() } }) } } func pullAllUsersCards() { cardArray.removeAll() let userRef = ref.child("users").child((user?.uid)!).child("cards") userRef.observe(DataEventType.value, with: { (snapshot) in for userscard in snapshot.children { let cardID = (userscard as AnyObject).key as String let cardRef = self.ref.child("cards").child(cardID) cardRef.observe(DataEventType.value, with: { (cardSnapShot) in let cardSnap = cardSnapShot as DataSnapshot let cardDict = cardSnap.value as! [String: AnyObject] let cardNickname = cardDict["nickname"] let cardType = cardDict["type"] let cardStatus = cardDict["cardStatus"] self.cardNicknameToTransfer = cardNickname as! String self.cardtypeToTransfer = cardType as! String let aCard = CardClass() aCard.cardID = cardID aCard.nickname = cardNickname as! String aCard.type = cardType as! String aCard.cStatus = cardStatus as! Bool self.cardArray.append(aCard) DispatchQueue.main.async { self.tableView.reloadData() } }) } }) } 

Answer 1

I got help and changed my code a lot, so now it works

 func checkIfDataExits() { self.ref.observe(DataEventType.value, with: { (snapshot) in if snapshot.hasChild("services") { self.pullCardData() } else { DispatchQueue.main.async { self.collectionView.reloadData() } } }) } func pullCardData() { let cardRef = self.ref.child("cards") cardRef.observe(DataEventType.value, with: { (snapshot) in for cards in snapshot.children { let allCardIDs = (cards as AnyObject).key as String if allCardIDs == self.cardID { if let childId = self.cardID { let thisCardLocation = cardRef.child(childId) thisCardLocation.observe(DataEventType.value, with: { (snapshot) in let thisCardDetails = snapshot as DataSnapshot if let cardDict = thisCardDetails.value as? [String: AnyObject] { self.selectedCard?.cardID = thisCardDetails.key self.selectedCard?.nickname = cardDict["nickname"] as? String ?? "" self.selectedCard?.type = cardDict["type"] as? String ?? "" self.pullServicesForCard() } }) } } } }) } func pullServicesForCard() { if let theId = self.cardID { let thisCardServices = self.ref.child("cards").child(theId).child("services") thisCardServices.observe(DataEventType.value, with: { (serviceSnap) in if self.serviceArray.count != Int(serviceSnap.childrenCount) { self.serviceArray.removeAll() self.fetchAndAddAllServices(serviceSnap: serviceSnap, index: 0, completion: { (success) in if success { DispatchQueue.main.async { self.collectionView.reloadData() } } }) } }) } } func fetchAndAddAllServices(serviceSnap: DataSnapshot, index: Int, completion: @escaping (_ success: Bool) -> Void) { if serviceSnap.hasChildren() { if index < serviceSnap.children.allObjects.count { let serviceChild = serviceSnap.children.allObjects[index] let serviceID = (serviceChild as AnyObject).key as String let thisServiceLocationInServiceNode = self.ref.child("services").child(serviceID) thisServiceLocationInServiceNode.observeSingleEvent(of: DataEventType.value, with: { (thisSnap) in let serv = thisSnap as DataSnapshot if let serviceDict = serv.value as? [String: AnyObject] { let aService = ServiceClass(serviceDict: serviceDict) self.serviceCurrent = serviceDict["serviceStatus"] as? Bool self.serviceName = serviceDict["serviceName"] as? String ?? "" self.serviceURL = serviceDict["serviceURL"] as? String ?? "" self.serviceFixedBool = serviceDict["serviceFixed"] as? Bool self.serviceFixedAmount = serviceDict["serviceAmount"] as? String ?? "" self.attentionInt = serviceDict["attentionInt"] as? Int self.totalArr.append((serviceDict["serviceAmount"] as? String)!) // self.doubleArray = self.totalArr.flatMap{ Double($0) } // let arraySum = self.doubleArray.reduce(0, +) // self.title = self.selectedCard?.nickname ?? "" // if let titleName = self.selectedCard?.nickname { // self.title = "\(titleName): \(arraySum)" // } aService.serviceID = serviceID if serviceDict["serviceStatus"] as? Bool == true { self.selectedCard?.cStatus = true } else { self.selectedCard?.cStatus = false } if !self.serviceArray.contains(where: { (service) -> Bool in return service.serviceID == aService.serviceID }) { self.serviceArray.append(aService) self.serviceArray.sort {$1.serviceAttention < $0.serviceAttention} } } self.fetchAndAddAllServices(serviceSnap: serviceSnap, index: index + 1, completion: completion) }) } else { completion(true) } } else { completion(false) } }