swift - Geofire/Firebase 函数正在快速执行处理程序多次

Question

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

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

然后在CollectionView中使用Userarray，问题是当CollectionView显示它只显示一个 User 对象。

我在代码中放置了一些 print() 行进行调试，并发现每次附加项目时该函数都会通过 handler 传递数据，因此当到达显示 CollectionView 的 VC 时，数组的计数为 1。

将以下行移动到 for 循环 括号之外会传递一个空的数组

如何更新我的函数，以便仅调用一次处理程序并传递完整的数组？

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

这是函数:

    //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

对于地理查询范围内的每个键都会触发 .keyEntered 事件。因此，最初这意味着它会对范围内的所有键触发，从那一刻起，只要有新键进入范围，它就会触发(即，如果您在范围内添加新用户，或者用户移动到范围内)。

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

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 删除观察者的好时机>.

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