在 Cloud Firestore (Swift) 中运行 collectionGroup 查询时崩溃

Question

我使用 Swift、SwiftUI 和 Cloud Firestore 运行一个移动应用项目，我需要根据用户的不同设置/偏好来找到他们。我已经通过使用 collectionGroup 查询解决了这个问题。但有时（可能 10 次中的 1 次）查询崩溃而没有任何（对我而言）可理解的错误消息。复合索引是使用 XCode 提供的 http 链接创建的。

这是我使用的功能：

func getUsersFromActivityPrefs(genders:[String], activities:[Int],skillScore_min:Int, skillScore_max:Int,completion:@escaping ([String]) -> ()) {
   
var matchUsers = [String]()
var count = 0
let db = Firestore.firestore()

for gender in genders {
    for activity in activities {
        let dbRef = db.collectionGroup("activity_preferences")
            .whereField("gender", isEqualTo: gender)
            .whereField("activityid", isEqualTo: activity)
            .whereField("status", isEqualTo: true)
            .whereField("skill_score", isGreaterThanOrEqualTo: skillScore_min)
            .whereField("skill_score", isLessThanOrEqualTo: skillScore_max)
            .limit(to: 100)
        dbRef.getDocuments {( snap, err) in
            count+=1
            if err != nil {
                print(err!.localizedDescription)
            }
            for i in snap!.documentChanges{
                let uid = i.document.get("uid") as? String ?? ""
                if uid != "" && !matchUsers.contains(uid) {
                    matchUsers.append(uid)
                    if matchUsers.count == 100 {
                        count = genders.count * activities.count
                        completion(matchUsers) //escaping completion handler
                        return
                    }
                }
            }
            if count == genders.count * activities.count {
                completion(matchUsers)
                return
            }
        }
    }
}

}

我附上了来自 XCode 的跟踪日志和崩溃消息。我使用最新版本的 Firebase SDK，部署目标是 iOS14。 这是我得到的跟踪日志：

线程 #1，队列 = 'com.apple.main-thread'，停止原因 = EXC_BAD_ACCESS（代码=1，地址=0x4f） 帧#0：0x00007fff4b80dd66 AttributeGraphAG::Graph::input_value_ref_slow(AG::data::ptr<AG::Node>, AG::AttributeID, unsigned int, AGSwiftMetadata const*, bool*, long) + 322 frame #1: 0x00007fff4b81f1a5 AttributeGraphAGGraphGetValue + 203 帧 #2: 0x00007fff55e7ffab SwiftUISwiftUI.DynamicBody.phase.getter : SwiftUI._GraphInputs.Phase + 27 frame #3: 0x00007fff55e80176 SwiftUISwiftUI.DynamicBody.updateValue() -> () + 294 帧 #4: 0x00007fff55b9583a SwiftUIpartial apply forwarder for implicit closure #2 (Swift.UnsafeMutableRawPointer, __C.AGAttribute) -> () in implicit closure #1 (A1.Type) -> (Swift.UnsafeMutableRawPointer, __C.AGAttribute) -> () in closure #1 () -> (Swift.UnsafeMutableRawPointer, __C.AGAttribute) -> () in closure #1 (Swift.UnsafePointer<A1>) -> AttributeGraph.Attribute<A> in AttributeGraph.Attribute.init<A where A == A1.Value, A1: AttributeGraph.StatefulRule>(A1) -> AttributeGraph.Attribute<A> + 26 frame #5: 0x00007fff4b808d03 AttributeGraphAG::Graph::UpdateStack::update() + 505 帧 #6: 0x00007fff4b809199 AttributeGraphAG::Graph::update_attribute(AG::data::ptr<AG::Node>, bool) + 335 frame #7: 0x00007fff4b80d8e8 AttributeGraphAG::Graph::value_ref(AG::AttributeID, AGSwiftMetadata const*, bool*) + 130 第 8 帧：0x00007fff4b81f1f3 AttributeGraphAGGraphGetValue + 281 frame #9: 0x00007fff561aeeb7 SwiftUISwiftUI.GraphHost.updatePreferences() -> Swift.Bool + 39 帧 #10: 0x00007fff55c9a8cf SwiftUISwiftUI.ViewGraph.updateOutputs(at: SwiftUI.Time) -> () + 95 frame #11: 0x00007fff5611310c SwiftUIclosure #1 () -> () in (SwiftUI 中的扩展):SwiftUI.ViewRendererHost.render(interval: Swift.Double, updateDisplayList: Swift.Bool) -> () + 1308 框架 #12: 0x00007fff56112327 SwiftUI(extension in SwiftUI):SwiftUI.ViewRendererHost.render(interval: Swift.Double, updateDisplayList: Swift.Bool) -> () + 343 frame #13: 0x00007fff55ba07de SwiftUIclosure #1 () -> () in SwiftUI._UIHostingView.requestImmediateUpdate() -> () + 62 第 14 帧：0x00007fff562739ae SwiftUIreabstraction thunk helper from @escaping @callee_guaranteed () -> () to @escaping @callee_unowned @convention(block) () -> () + 14 frame #15: 0x0000000112ebd8ac libdispatch.dylib_dispatch_call_block_and_release + 12 帧#16：0x0000000112ebea88 libdispatch.dylib_dispatch_client_callout + 8 frame #17: 0x0000000112eccf23 libdispatch.dylib_dispatch_main_queue_callback_4CF + 1152 第 18 帧：0x00007fff203a8276 CoreFoundation__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9 frame #19: 0x00007fff203a2b06 CoreFoundation__CFRunLoopRun + 2685 帧 #20：0x00007fff203a1b9e CoreFoundationCFRunLoopRunSpecific + 567 frame #21: 0x00007fff2b773db3 GraphicsServicesGSEventRunModal + 139 帧 #22: 0x00007fff24660af3 UIKitCore-[UIApplication _run] + 912 frame #23: 0x00007fff24665a04 UIKitCoreUIApplicationMain + 101 第 24 帧：0x000000010db84a5b 陪练main at AppDelegate.swift:14:7 frame #25: 0x00007fff20257415 libdyld.dylibstart + 1

附件： XCode 崩溃1 综合指数2

Answer 1

func getUsersFromActivityPrefs(genders: [String], activities: [Int], skillScore_min: Int, skillScore_max: Int, completion: @escaping ([String]) -> Void) {
    var matchUsers = [String]()
    var count = 0
    let db = Firestore.firestore()
    let dispatch = DispatchGroup() // instantiate dispatch group outside loop
    
    for gender in genders {
        for activity in activities {
            dispatch.enter() // enter group on each iteration
            
            let dbRef = db.collectionGroup("activity_preferences")
                .whereField("gender", isEqualTo: gender)
                .whereField("activityid", isEqualTo: activity)
                .whereField("status", isEqualTo: true)
                .whereField("skill_score", isGreaterThanOrEqualTo: skillScore_min)
                .whereField("skill_score", isLessThanOrEqualTo: skillScore_max)
                .limit(to: 100)
            
            dbRef.getDocuments {( snap, err) in
                if let snap = snap {
                    count += 1
                    
                    for doc in snap.documents {
                        if let uid = doc.get("uid") as? String,
                           !matchUsers.contains(uid) {
                            matchUsers.append(uid)
                        }
                    }
                } else if let err = err {
                    print(err)
                }
                
                dispatch.leave() // always leave no matter what the db returned
            }
        }
    }
    
    /*
     this is the group's completion handler and it's only
     called once after all groups have entered and left
     */
    dispatch.notify(queue: .main) {
        completion(matchUsers)
    }
}