在一个iOS/SWIFT项目中，如何防止页面的流程压倒其过渡到的页面？

Question

我的意思是您在第A页上。按钮按导航控制器到第B。A页上的过程非常密集且压倒性页面B到产生错误的UI结果（重复的单​​元格或缺失单元格）

i在大约100次测试中仅观察到这些错误的结果两次。当我按下一个疯狂的按钮时，他们俩都发生了时间页B加载。

我最初以为我在B页上遇到了种族问题，但我不认为这可能是原因，因为此错误仅在A页极不知所措时才发生。我不希望在第B页上使用骨骼视图。以下是第B页中的代码，该代码确定了要显示的单元格的用户。这两个错误，其中1）复制用户的单元格和2）并非所有用户都在单元格中表示。

在ViewDidload中：

if CLLocationManager.locationServicesEnabled() {
switch(CLLocationManager.authorizationStatus()) {
case .authorizedAlways, .authorizedWhenInUse:
    print("Access")
    locationManager.delegate = self
    if CLLocationManager.locationServicesEnabled() {
        locationManager.delegate = self
        locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters
        locationManager.startUpdatingLocation()
    }
    let uid = Auth.auth().currentUser!.uid
    let thisUserRef = Database.database().reference().child("user").child(uid)
    let myuserRef = thisUserRef.child("userWhoLike")
    var handle: UInt = 0
    handle = myuserRef.queryLimited(toLast: 30).observe(DataEventType.value,  with: {  snapshot in
        print("kkkkk")
        func decode(autoId: String) -> TimeInterval {
            ...
            return TimeInterval(exactly: timestamp)!
        }
        let uniqueArray1 = snapshot.children.allObjects as! [DataSnapshot]
        let userArray = Array(Set(uniqueArray1))
        for person4 in userArray where uid == Auth.auth().currentUser?.uid   {
            self.dg.enter()
            let personUid = person4.value as! String
            let planDict18 = person4.key
            let time22 = decode(autoId: planDict18)
            let time11 = Int(time22)
            self.dg.leave()
            self.dg.notify(queue: .main) {
                let date = Date(timeIntervalSince1970: TimeInterval(time11)/1000.0)
                if Calendar.current.isDateInToday(date){
                    self.printPersonInfo(uid: personUid)
                }
            }
        }
        DispatchQueue.main.asyncAfter(deadline: .now() + 4) {
            let ref = Database.database().reference().child("user")
            ref.removeObserver(withHandle: handle)
            ref.removeObserver(withHandle: self.handleA)
        }
    })
case .notDetermined:
    print("Location services are not enabled")
 } else {
print("Location services are not enabled")
}