Swift iOS Firebase - 如何结合 queryOrdered(byChild) 和 GeoFire observe(.keyEntered) 来同时获取快照和位置结果？

Posted 2023-03-13

【中文标题】Swift iOS Firebase - 如何结合 queryOrdered(byChild) 和 GeoFire observe(.keyEntered) 来同时获取快照和位置结果？

【英文标题】：Swift iOS Firebase -How to Combine a queryOrdered(byChild) and GeoFire observe(.keyEntered) to get a snapshot and location result at the same time?

【发布时间】：2018-10-27 17:55:47

【问题描述】：

使用UISearchController 如果我想搜索用户最喜欢的书名是哈利波特的书，我会执行以下操作来获取快照：

func updateSearchResults(for searchController: UISearchController) 

    // the searchText the user entered is Harry Potter
    guard let searchText = searchController.searchBar.text?.lowercased() else  return 

    let favoriteBooksRef = Database.database().reference().child("searchFavoriteBooks").queryOrdered(byChild: "titleLowercased").queryStarting(atValue: searchText).queryEnding(atValue: searchText+"\uf8ff")

    favoriteBooksRef.observeSingleEvent(of: .value, with:  (snapshot) in
        ...
    )

如果我想在某个位置搜索用户，我会使用 GeoFire 执行以下操作：

let geofireRef = Database.database().reference().child("users_locations")
let geoFire = GeoFire(firebaseRef: geofireRef)
let center = CLLocation(latitude: myLat, longitude: myLon)

let circleQuery = geoFire.query(at: center, withRadius: 5)

var queryHandler = circleQuery.observe(.keyEntered, with:  (key: String!, location: CLLocation!) in
       ...
)

我如何使用 UISearchController 来组合这两个查询，以便我可以在距离我所在的位置 5 公里范围内获取所有拥有最喜欢的哈利波特书名的用户的快照？

根据to this link，该人说只需在GFQueryResultBlock 中添加第三个参数作为快照，但它没有解释该快照如何到达不同的节点以从中提取数据。

我的数据库（它显示了 1 个用户，但附近可能有 20 个用户会出现在搜索结果中）：

-root
   |
   @--users
   |    |
   |    @---uid789
   |          |
   |          |--username: "avidBookReader"
   |          |--lat: 34.111
   |          |--lon: -34.222
   |          @---postId001
   |                  |
   |                  |--title: "Harry Potter"
   |
   @--users_location
   |    |
   |    @---uid789
   |          |
   |          |--g: xyz234
   |          @--l:      
   |              |--0: 34.111
   |              |--1: -34.222
   |
   @--searchFavoriteBooks
        |
        @---postId001
               |
               |--uid: "uid789"
               |--titleLowercased: "harry potter"
               |--lat: 34.111
               |--lon: -34.222

到目前为止我尝试了什么。我基本上首先检查了所有最接近设备的用户，然后将它们放入名为usersInRadius 的数组中。之后，我检查了在搜索栏中输入的文本上运行的查询，并将这些结果添加到名为 favoriteBooks 的数组中。我将它们都转换为 Set 并尝试使用 Set 的 .intersection() 函数比较其中包含的项目但未成功，我收到警告

调用'intersection'的结果未被使用

然后，我将该函数的最终结果放入名为 finalResults 的数组中，以显示在 collectionView 中。

搜索有效，我从 finalResults 数组中获得了哈利波特书籍，但对我附近的用户的过滤并没有过滤掉每一本。我认为问题发生在第 19 步：

favoriteBooksAsSet.intersection(usersInRadiusAsSet) // I get the warning message above

过滤不正确。这是下面的代码。

let radius: Double = 5.0
let usersInRadius = [SearchModels] // an arr of all the users in the vicinity 
let favoriteBooks = [SearchModels] // an arr of all the results that contain the searchText
let finalResults = [SearchModels] // the final array that will display the results of the users in the vicinity with the search text by comparing the 2 above arrays as Sets

// 1. user enters text into the searchBar
func updateSearchResults(for searchController: UISearchController) 

    // 2. the text is Harry Potter
    guard let searchText = searchController.searchBar.text?.lowercased() else  return 

    // 3. look for all the users in the devices proximity
    getAlltheUsersInTheChosenRadius(radius: radius, searchText: searchText)
 

func getAlltheUsersInTheChosenRadius(radius: Double, searchText: String) 

    // 4. check for location authorization
    if (CLLocationManager.authorizationStatus() == .authorizedWhenInUse ||
        CLLocationManager.authorizationStatus() ==  .authorizedAlways) 

        currentLocation = locationManager.location

        // 5. get the device's lat and lon
        let myLat = currentLocation.coordinate.latitude
        let myLon = currentLocation.coordinate.longitude

        // 6. use them to create a CLLocation
        let center = CLLocation(latitude: myLat, longitude: myLon)

        // 7. create the geoFire node to search on
        let geofireRef = Database.database().reference().child("users_location")
        let geoFire = GeoFire(firebaseRef: geofireRef)

        // 7. center in a 5 meter radius
        let circleQuery = geoFire.query(at: center, withRadius: radius)

        // 8. get the .keyEntered info
        let queryHandler = circleQuery.observe(.keyEntered, with: 
            (key: String!, location: CLLocation!) in

            // 9. create a SearchModel object and set the key to the userId's key and the location to the location
            let searchModel = SearchModel()
            searchModel.userId = key
            searchModel.location = location

            // 10. append these objects to an array of all the users who are in the vicinity      
            self.usersInRadius.append(searchModel)
        )

        // 11. geoFire is done now query the searchText
        circleQuery.observeReady(

            self.queryTheSearchFavoriteBooksNode(searchText: searchText)
        )
    


func queryTheSearchFavoriteBooksNode(searchText: searchText) 

    // 12. set the ref for the searchFavoriteBooks to search on
    let favoriteBooksRef = Database.database().reference().child("searchFavoriteBooks").queryOrdered(byChild: "titleLowercased").queryStarting(atValue: searchText).queryEnding(atValue: searchText+"\uf8ff")

    favoriteBooksRef.observeSingleEvent(of: .value, with:  (snapshot) in

        guard let dictionaries = snapshot.value as? [String: Any] else 
            self.finalResults.removeAll()
            self.collectionView.reloadData()
            return
        

        // 14. grab all the key/values pairs that have a value named "harry potter"
        dictionaries.forEach( (key, value) in

            guard let dict = value as? [String: Any] else  return 

            // 15. init a SearchModel with the values from the dict
            let searchModel = SearchModel(dict: dict)

            // 16. check if the result is in the favoriteBooks array
            let isContained = self.favoriteBooks.contains(where:  (post) -> Bool in
                return searchModel.userId == post.userId
            )

            // 17. if it's not in the favoriteBooks array the append it to it
            if !isContained 
                self.favoriteBooks.append(searchModel)

                if self.favoriteBooks.count > 1 

                    // 18. if there is more then 1 item in the favoriteBooks then cast it as a Set and also cast the userInRadius from step 10 as a Set
                    let favoriteBooksAsSet = Set(self.favoriteBooks)
                    let usersInRadiusAsSet = Set(self.usersInRadius)

                    // 19. compare the items in both sets and remove what I don't want. This ISN'T working
                   favoriteBooksAsSet.intersection(usersInRadiusAsSet)

                    // 20. append the results from the favoriteBooksAsSet in step 19 to the final finalResults which should display the UISearchController's results
                    self.finalResults.append(contentsOf: Array(favoriteBooksAsSet))
                
                self.collectionView?.reloadData()
            
        )
    )


// this is the SearchModel
class SearchModel: : Equatable, Hashable 

    var hashValue: Int 
        guard let uid = userId, let loc = location else 
            return Int(arc4random())
        
        return uid.djb2hash ^ loc.hashValue
    

    var postId: String?
    var title: String?
    var userId: String?
    var location: CLLocation?
    var lat: CLLocationDegrees?
    var lon: CLLocationDegrees?

    convenience init(dict: [String: Any]) 
        self.init()

        postId = dict["postId"] as? String
        title = dict["title"] as? String
        userId = dict["userId"] as? String
        location = dict["location"] as? CLLocation
        lat = dict["lat"] as? CLLocationDegrees
        lon = dict["lon"] as? CLLocationDegrees
    

    static func == (lhs: SearchModel, rhs: SearchModel) -> Bool 
        return lhs.userId == rhs.userId
    


// String extension for the hash value in the SearchModel
extension String 
    var djb2hash: Int 
        let unicodeScalars = self.unicodeScalars.map  $0.value 
        return unicodeScalars.reduce(5381) 
            ($0 << 5) &+ $0 &+ Int($1)
        
    

【参考方案1】：

我收到了answer from this SO answer

问题在于我在第 18 步和第 19 步分离了集合：

// 18. if there is more then 1 item in the favoriteBooks then cast it as a Set and also cast the userInRadius from step 10 as a Set
let favoriteBooksAsSet = Set(self.favoriteBooks)
let usersInRadiusAsSet = Set(self.usersInRadius)

// 19. compare the items in both sets and remove what I don't want. This ISN'T working
favoriteBooksAsSet.intersection(usersInRadiusAsSet)

// 20. append the results from the favoriteBooksAsSet in step 19 to the final finalResults which should display the UISearchController's results
self.finalResults.append(contentsOf: Array(favoriteBooksAsSet))
            

更正解决方案是使用 SO 答案中的内容并将两个数组组合为 Set，然后无论交集方法的结果如何，都将其放入步骤 20：

// steps 18 and 19 combined
let tempSet = Set(self.favoriteBooks).intersection(Set(self.usersInRadius))

// 20. append the results from the tempSet in step 18 and 19 to the final finalResults which should display the UISearchController's results
self.finalResults.append(contentsOf: Array(tempSet))