Question

我有一个功能，可以根据用户的当前位置显示MKMapView上的引脚。此功能利用了GeoFire的GFQuery：

// Allows the user to scroll on the map and have the parties update
func mapView(_ mapView: MKMapView, regionWillChangeAnimated animated: Bool) {
    let loc = CLLocation(latitude: mapView.centerCoordinate.latitude, longitude: mapView.centerCoordinate.longitude)

    showPartiesOnMap(location: loc)

}

从代码片段中可以看到，此函数在地图上重复调用showParties（每次更新位置）。该函数如下所示：

func showPartiesOnMap(location:CLLocation) {
    circleQuery = geoFire?.query(at: location, withRadius: 2.5)

    // Observe whenever we find a sighting. If there are 50 parties, this will be called 50 times
    partyObserve = circleQuery?.observe(GFEventType.keyEntered, with: { (key, location) in

        if let location = location, let key = key {

            let anno: PartyAnnotation


            self.fullPartyName = key

            // Attempting to print just the name of the party and not the time
            var characters = Array(key.characters)

            var currentChar: Character = " "
            var finalName: String = ""
            var dateString: String = ""
            var finalDate: Date? = nil


            // Gets the name of the party
            currentChar = characters.remove(at: 0)
            while currentChar != "*" {

                finalName += "\(currentChar)"
                currentChar = characters.remove(at: 0)
            }

            // Gets the date the party was created
            currentChar = characters.remove(at: 0)
            while currentChar != "*" {
                dateString += "\(currentChar)"
                currentChar = characters.remove(at: 0)
            }

            let dateFormatter = DateFormatter()
            dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss Z"
            finalDate = dateFormatter.date(from: dateString)!

            // Check if the party should still exist
            if(self.shouldBeDeleted(partyDate: finalDate!)) {
                self.geoFire.removeKey(key)
            }
            else if characters.count > 0 {
                // The party in question is public
            }
            else {
                // Created an annotation because the party should not be deleted
                anno = PartyAnnotation(coordinate: location.coordinate, partyName: finalName)

                self.mapView.addAnnotation(anno)

            }

        }

    })

}

我面临的问题是，当用户离开此页面时，我将无法再正确观察Firebase上的任何内容。对于以后的任何观察（非GeoFire），我在展开一个可选值时都会收到意外发现的nil。

经过一堆测试，我得出的结论是问题出在线路上：

partyObserve = circleQuery?.observe(GFEventType.keyEntered, with: { (key, location) in

如果我注释掉该观察结果，则不会发生此问题。不幸的是，我需要此功能，因此将其注释掉不是可行的解决方案。我试图删除AllObservers并使用Firebase Handles删除观察值。有谁知道为什么会发生这种情况或可能的解决方案？

预先感谢您的帮助！

GeoFire查询后无法正确观察Firebase

0 个答案: