Geofire/Firebase 函数在 swift 中多次执行处理程序

Question

我有以下函数，它使用 Geofire 获取用户列表，然后在嵌套设置中使用 Firebase 查询。

我首先执行 Geofire 查询以获取 key，然后执行 Firebase 查询并创建与 key 匹配的 User 对象，并将 User 附加到一个数组，然后通过handler。

然后将User array 用于CollectionView，问题是当CollectionView 显示时它只显示一个User 对象。

我在代码中放置了一些 print() 行以进行调试，并发现该函数在每次附加项目时都通过 handler 传递数据，因此数组的计数达到 @显示CollectionView的987654333@是1。

将以下行移到for loop 括号外传递一个空的array

如何更新我的函数以使 handler 仅被调用一次并传递完整的 array？

handler(self.shuffleArray(array: filteredUsers) as! [User], true)

函数如下：

    //Fetches all users currently at a Venue location of radius 50 metres
func getUsersAtVenue(forVenueLocation venueLocation: CLLocation, forUid uid: String, handler: @escaping (_ users: [User], _ success: Bool) -> ()){

    print("uid: \(uid)")

    var users = [User]()

    guard let currentLocation = LocationSingleton.sharedInstance.lastLocation else { return}//get current user's (device) location

    let distanceApart = round(10 * (venueLocation.distance(from: currentLocation) / 1000)) / 10 //get distance between currentLocation and venueLocation and convert from Mts to Kms rounding to 2 decimals

    if distanceApart <= 50 { //if distance apart if within 50kms then proceed

        let query = self.GEOFIRE_USERS_LOC.query(at: currentLocation, withRadius: 50)//radius in Kms

        query.observe(.keyEntered) { (key: String!, userLocation: CLLocation!) in

            print(key)

            self.REF_USERS.observeSingleEvent(of: .value, with: { (snapshot) in

                guard let usersSnapshot = snapshot.children.allObjects as? [DataSnapshot] else { return }

                for user in usersSnapshot{

                    let discoverable = user.childSnapshot(forPath: "discoverable").value as! Bool

                    if user.key == key && discoverable == true {

                        let uid = user.key
                        let name = user.childSnapshot(forPath: "name").value as! String
                        let email = user.childSnapshot(forPath: "email").value as! String
                        let profilePictureURL = user.childSnapshot(forPath: "profilePictureURL").value as! String

                        let birthday = user.childSnapshot(forPath: "birthday").value as! String
                        let firstName = user.childSnapshot(forPath: "firstName").value as! String
                        let lastName = user.childSnapshot(forPath: "lastName").value as! String
                        let gender = user.childSnapshot(forPath: "gender").value as! String
                        let discoverable = user.childSnapshot(forPath: "discoverable").value as! Bool
                        let online = user.childSnapshot(forPath: "online").value as! Bool

                        let dictionary: [String : Any] = ["uid": uid, "name": name, "email": email, "profilePictureURL": profilePictureURL, "birthday": birthday, "firstName": firstName, "lastName": lastName, "gender": gender, "discoverable": discoverable, "online": online]

                        let user = User(uid: uid, dictionary: dictionary)

                        users.append(user)

                    }//end if

                }//end for

                //filter out current user from array
                let filteredUsers = users.filter({ (user: User) -> Bool in return !user.uid.contains(uid) })

                print("filteredUsers count: \(filteredUsers.count)")

                //handler passing a shuffled version of the array
                handler(self.shuffleArray(array: filteredUsers) as! [User], true)

            })//end FIR snapshot call

        }//end geoquery


    } else {//if distanace apart is NOT within 50kms then do this
        print("You're too far apart.")
        handler(users, false)
    }



}//end func

控制台：

uid: dBQd541pxlRypR7l1WT2utKVxdX2
some("dBQd541pxlRypR7l1WT2utKVxdX5")
some("dBQd541pxlRypR7l1WT2utKVxdX3")
some("dBQd541pxlRypR7l1WT2utKVxdX2")
some("dBQd541pxlRypR7l1WT2utKVxdX4")
filteredUsers count: 1
users count: 1
filteredUsers count: 2
users count: 2
filteredUsers count: 2
users count: 2
filteredUsers count: 3
users count: 3

Answer 1

.keyEntered 事件会针对您的地理查询范围内的每个键触发。所以最初这意味着它会为范围内的所有键触发，从那一刻起，只要有新键进入范围（即，如果您在范围内添加新用户，或者如果用户移动到范围内），它就会触发。

听起来您想检测何时为所有初始用户调用了 .keyEntered。为此，您可以观察 ready 事件。

query.observeReadyWithBlock({
    //handler passing a shuffled version of the array
    handler(self.shuffleArray(array: filteredUsers) as! [User], true)
})

如果您对在初始查询后获取新用户/移动用户的更新不感兴趣，这也是通过调用 removeObserverWithFirebaseHandle 或 removeAllObservers 删除您的观察者的好时机。

另请参阅 Geofire 文档中的 waiting for queries to be 'ready'。