ios - firebase 查询返回错误的快照

Question

所以我有一个使用 firebase 的应用程序。在此应用程序中，我想抓取结束时间大于或等于当天的事件。我创建了这个函数，我相信它可以实现这一点。但是，它什么也没返回

static func show(forEventKey eventKey: String, completion: @escaping (Event?) -> Void) {
    print(eventKey)
    let ref = Database.database().reference().child("events").child(eventKey)

    ref.queryOrdered(byChild: "end")
        .queryStarting(atValue: Date().timeIntervalSince1970, childKey: "end")
        .observeSingleEvent(of: .value, with: { (snapshot) in

            print(snapshot)

            guard let event = Event(snapshot: snapshot) else {
                return completion(nil)
            }

            completion(event)

        })
}

我的树中事件节点下的子项如下所示

"BEVT" : {
  "attend:count" : 5,
  "event:category" : "Seize The Night",
  "event:city" : "Philadelphia",
  "event:date" : {
    "end:date" : "06/18/2018",
    "end:time" : "7:01 PM",
    "start:date" : "06/17/2018",
    "start:time" : "12:01 PM"
  },
  "event:datetime" : {
    "end" : 1529362860,
    "start" : 1529251260
  },
  "event:description" : "Travis Scott is ready to hit the road. The 24-year-old hitmaker will embark on his Birds Eye View tour, powered by Live Nation, in support of his sophomore album and Billboard 200 No. 1 Birds in the Trap Sing McKnight.",
  "event:imageURL" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_flyers%2FtravisScott-compressor.png?alt=media&token=c6e46da1-1395-4a37-a8fc-3ff53d5c0d4d",
  "event:name" : "birds eye view tour",
  "event:promo" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/event_promo_vid%2FBEVT%2FTravis%20Scott_%20Houston%20Birds%20Eye%20View%20Tour%20Promo.mp4?alt=media&token=6d27d76e-281e-4083-a0ff-dbe2f25703e7",
  "event:state" : "PA",
  "event:street:address" : "5748 Baltimore Pike",
  "event:zip" : 19143
}

当我打印快照时，它看起来像这样，这表明它找到了它，但它没有返回整个快照

Snap (BEVT) {
    "event:datetime" =     {
        end = 1529445600;
        start = 1529442000;
    };
}

任何人都可以看到我的查询出了问题吗，因为我有点困惑？

我正在使用 geofire 获取 key ，因为我的应用程序是基于位置的。拿到这些 key 后，我会提取相关信息。我确信我无法改变 geofire 存储东西的方式。因此，我只剩下获取 key 并返回快照并根据当前日期创建事件对象。因此，基本上，如果事件结束日期晚于今天，则将其返回。如果没有就不要

我有这个 eventsbylocation 节点，它使用 geofire 根据位置获取 key 。假设我靠近 BEVT，它位于事件键中，geoFire 将抓取该键。现在事件位置节点不保存日期。通过 geofire 获取 key 后，我仅根据从 geofire 收到的 key 查询事件节点。我将如何基于此键集合进行查询，并仅返回基于该时间戳的特定日期之后的键。

"eventsbylocation" : {
    "ABP" : {
      ".priority" : "dr4e3nzh0q",
      "g" : "dr4e3nzh0q",
      "l" : [ 39.9840919, -75.1808035 ]
    },
    "BEVT" : {
      ".priority" : "dr4e0r56u7",
      "g" : "dr4e0r56u7",
      "l" : [ 39.9412882, -75.21873459999999 ]
    }

这是通过geoFire抓取 key 的函数

 static func showEvent(for currentLocation: CLLocation,completion: @escaping ([Event]) -> Void) {
        //getting firebase root directory
        var keys = [String]()
        var currentEvents = [Event]()
        var geoFireRef: DatabaseReference?
        var geoFire:GeoFire?
        geoFireRef = Database.database().reference().child("eventsbylocation")
        geoFire = GeoFire(firebaseRef: geoFireRef!)
        let circleQuery = geoFire?.query(at: currentLocation, withRadius: 17.0)
        circleQuery?.observe(.keyEntered, with: { (key: String!, location: CLLocation!) in
            print("Key '\(key)' entered the search area and is at location '\(location)'")
            if let currentKey = key {
                keys.append(currentKey)
            }
        })

        circleQuery?.observeReady({
            let dispatchGroup = DispatchGroup()
            for key in keys {
                dispatchGroup.enter()
                EventService.show(forEventKey: key, completion: { (event) in
                    if let currentEvent = event {
                        currentEvents.append(currentEvent)
                    }
                    dispatchGroup.leave()
                })
            }

            dispatchGroup.notify(queue: .main, execute: {
                print(currentEvents.count)
                completion(currentEvents)
            })

        })

    }

Answer 1

您的代码试图过于具体，并且您告诉它查看查询中数据的特定端 - 这没有意义，就好像您知道确切的路径一样，您不需要查询!

这是一个常见的误解 - 只需记住，查询需要提供父节点，然后提供您要查询的内容的子节点，因为然后它将迭代父节点下方的 child_nodes。

parent_node
  child_node
     child_node_of_what_you_are_querying
  child_node
     child_node_of_what_you_are_querying

所以你的查询应该是这样的。

 let ref = Database.database().reference().child("events").child("event_Key")

 ref.queryOrdered(byChild: "end")
    .queryStarting(atValue: Date().timeIntervalSince1970)
    .observeSingleEvent(of: .value, with: { (snapshot) in

     print(snapshot)

    })