从 Firebase 填充的 CLLocationCoordinate2D 数组不会保留其条目。斯威夫特 4

Posted 2023-03-14

【中文标题】从 Firebase 填充的 CLLocationCoordinate2D 数组不会保留其条目。斯威夫特 4

【英文标题】：CLLocationCoordinate2D array populated from Firebase doesn't keep it's entries. Swift 4

【发布时间】：2018-12-05 13:56:14

【问题描述】：

我对存储CLLocationCoordinates2D from retrieving posts from Firebase. Oddly the array gets populated every time I enterNewMapViewController. I thought that it would stay populated and only get new entries as the child observer send a new post from Firebase, but instead it's retrieving the posts every timeNewMapViewControllerloads. My problem is, that I get toNewMapViewControllereighter from a menu or from a notification action button. In the second case I usealertNotificationCoordinatesArrayin thecheckAlerts2`函数的@987654322`有问题，所以我需要它已经被填充但它是空的。

这里是代码中感兴趣的部分：

    override func viewDidLoad() 
        super.viewDidLoad()


        mapView.delegate = self
        locationManager.delegate = self
//        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation
        locationManager.distanceFilter = kCLDistanceFilterNone
        locationManager.allowsBackgroundLocationUpdates = true  //for getting user location in background mode as well

        mapView.showsUserLocation = true
        mapView.userTrackingMode = .follow   //map following user


//        let globalLocationManager: GlobalLocationManager
        configureLocationServices()
        addDoubleTap() // enabling duble tap gesture recognizer
//        mapView.isUserInteractionEnabled = true


        let location = locationManager.location?.coordinate

        if location == nil 
            return
        

        let region = MKCoordinateRegionMakeWithDistance(location!, 1000, 1000) // set mapView based on user location coordinates
        mapView.setRegion(region, animated: true)
        centerMapOnLocation()

        // alerts coordinates to post to Firebase
//        let alertDrawLatitude =  alertDrawCoordinates?.latitude    // not used ?
//        let alertDrawLomgitude = alertDrawCoordinates?.longitude   // not used ?
//        let title: String? = alertNotificationType                 // not used ?
//        var subtitle: String? = alertNotificationType              // not used ?

        //  user alert notification. takes coordinates from alertNotificationArray( populated with firebase returning coordinate for all alerts

         displayAlerts()

        print("alertNotificationCoordinatesArray at loading NewMapViewController is\(alertNotificationCoordinatesArray)")

        // if coming from alert notification
        if NewMapViewController.checkCounter > 0 
            checkAlerts2()
         else  return 


    

使用 Firebase 帖子的函数：

func displayAlerts()  

        ref = Database.database().reference()

        databaseHandle = ref?.child("Community").child("Alert Notifications").observe(.childAdded, with:  (snapshot) in

            //            defer  self.dummyFunctionToFoolFirebaseObservers() 
            guard let data = snapshot.value as? [String:String] else  return 
            guard let firebaseKey = snapshot.key as? String else  return 
            //                let date = data!["Date"]
            //                let time = data!["Time"]
            let dataLatitude = data["Latitude"]!
            let dataLongitude = data["Longitude"]!

            let type = data["Description"]!
            let id = Int(data["Id"]!)
            let doubledLatitude = Double(dataLatitude)
            let doubledLongitude = Double(dataLongitude)
            let recombinedCoordinate = CLLocationCoordinate2D(latitude: doubledLatitude!, longitude: doubledLongitude!)

            print("Firebase alerts posts retrieved")

//            print("Longitude Actual DataKey is \(String(describing: firebaseKey))")

//            print("fir long \((snapshot.value!, snapshot.key))")
            let userAlertAnnotation = UserAlert(type: type, coordinate: recombinedCoordinate, firebaseKey: firebaseKey, title: type,id: id!)
            self.userAlertNotificationArray.append(userAlertAnnotation)  // array of notifications coming from Firebase
            print("userAlertNotificationArray after retrieving from Firebase is : \(self.userAlertNotificationArray)")

            self.alertNotificationCoordinatesArray.append(recombinedCoordinate) // array for checkig alerts on route
             print("alertNotificationCoordinatesArray after retrieving from Firebase is : \(self.alertNotificationCoordinatesArray)")
            self.mapView.addAnnotation(userAlertAnnotation)

        )
    

以及来自控制台的打印：

alertNotificationCoordinatesArray at loading NewMapViewController is[]
Firebase alerts posts retrieved
userAlertNotificationArray after retrieving from Firebase is : [<fix_it_mapView.UserAlert: 0x1599f2e60>]
alertNotificationCoordinatesArray after retrieving from Firebase is : [__C.CLLocationCoordinate2D(latitude: 44.50139585197814, longitude: 11.335974854073397)]
CLLocationCoordinate2D(latitude: 44.50139585197814, longitude: 11.335974854073397)

如何修复这个被清空的数组？

【问题讨论】：

因为alertNotificationCoordinatesArray 每当你返回这个视图时都会被清空，这让我觉得这个视图正在重新定义一个新的属性。 alertNotificationCoordinatesArray 在哪里定义？它是你班级的财产吗？你在这个类中有viewDidAppear(_:) 函数吗？

@guard 工作其他恐慌。 alertNotificationCoordinatesArray 在 NewMapViewControllerclass 中定义，它没有 viewDidApear()function 。我应该更改什么以使其保持这些值？

你能显示定义alertNotificationCoordinatesArray 的行吗？如果它是NewMapViewController 的属性，则在视图被关闭时它将丢失。另外，我会检查在应用程序的生命周期中调用了多少次viewDidLoad()。每次视图加载时，它都可以通过调用displayAlerts() 来设置多个观察者。

@guard 工作其他恐慌。我懂了。作为NewMapViewController it gets emptied or just instantiated multiples times? viewDidLoad()gets called Avery time I get to NewMapViewController. How would I check it? should I calldisplayAlertsfrom a viewVillApear()`的属性？

对，如果您希望 alertNotificationCoordinatesArray 在 NewMapViewController 被解除并再次呈现后仍然存在，则需要将其保留在其他位置，例如 model class。

【参考方案1】：

感谢@guard 工作 else panic 指出每次我离开 VC 时我的数组都会被清空，因此解决方案只需将其放在单独的 swift 文件的结构中。

import Foundation
import CoreLocation



struct MapArray 
    static var alertNotificationCoordinatesArray: [CLLocationCoordinate2D] = []  //  alert notification array coordinates only used to draw alerts on map and find route obstacles