CKQueryOperation queryCompletionBlock 未调用

Question

I'm using a CKQueryOperation that apparently works fine for most of my users. However, for some of them it is not working. The issue is that queryCompletionBlock is not being called.

Analysing user logs I can see that it works fine for most of the users, but it doesn't work for a few of them. It fails in all kind of iPhone models. But iOS is always iOS 14.2 on the failing devices. Unfortunately, I can not reproduce the issue on my device and this makes impossible to debug it.

I've already checked that the issue is not related with the internet connection type (wifi or data)

Any idea?

This is the code

func fetchTeams(_ success: @escaping (_ result: [CKRecord]?) -> Void,
                       failure: @escaping (_ error: NSError) -> Void) {
        
        bfprint("fetchTeams starts")
        let type = RecordType.Team
        let predicate = NSPredicate(format: "TRUEPREDICATE")
        let query = CKQuery(recordType: type.rawValue, predicate: predicate)
        let operation = CKQueryOperation(query: query)
        allTeamsRecords = []
        executeQueryOperation(operation,
                                   success: success,
                                   failure: failure)
    }
    
    private func executeQueryOperation(_ queryOperation: CKQueryOperation,
                                              success: @escaping (_ result: [CKRecord]?) -> Void,
                                              failure: @escaping (_ error: NSError) -> Void) {
        
        bfprint("executeQueryOperation starts")
        
        let configuration = CKOperation.Configuration()
        configuration.qualityOfService = .userInitiated
        queryOperation.configuration = configuration
        queryOperation.queuePriority = .veryHigh

        queryOperation.recordFetchedBlock = { [weak self] (record) in
            guard let strongSelf = self else {
                bfprint("CloudKitDataProvider was deallocated before we got all team records")
                return
            }
            strongSelf.allTeamsRecords.append(record)
        }
        
        queryOperation.queryCompletionBlock = { [weak self] (cursor, error) in
            bfprint("fetch teams operation completion block called")
            if let cursor = cursor {
                bfprint("We got a new cursor fetching teams")
                let newOperation = CKQueryOperation(cursor: cursor)
                guard let strongSelf = self else {
                    bfprint("CloudKitDataProvider was deallocated before we got all team records")
                    return
                }
                strongSelf.executeQueryOperation(newOperation,
                                           success: success,
                                           failure: failure)
            }
            else if let error = error {
                DispatchQueue.main.async(execute: {
                    failure(error as NSError)
                    bfprint("Cloud Query Error - Fetching Teams): \(error)")
                })
            }
            else {
                DispatchQueue.main.async(execute: {
                    bfprint("Get teams finished successfully")
                    guard let strongSelf = self else {
                        bfprint("CloudKitDataProvider was deallocated before we execute success closure")
                        return
                    }
                    success(strongSelf.allTeamsRecords)
                })
            }
        }
        Self.publicDB.add(queryOperation)
        bfprint("query added to database")
    }

Answer 1

I don't know what's specifically wrong in your situation, but I might offer some general guidance with CloudKit as I've worked with it over the years. CloudKit is really reliable, but it's also a little unreliable. :)

Here are some tips:

• Build in mechanisms to repeatedly check that you have the latest data.
• Background notifications don't always come. Have a way to get data that may have been missed.
• Development and production behave a little differently in that dev seems to be a bit less reliable overall.
• The CloudKit Dashboard needs to be refreshed (like the whole page in your web browser) from time-to-time because the state shown can get stale even when using the reload and query buttons in the interface.

So in your case, you might have a way to repeatedly try the CKQueryOperation so that it gets reattempted if something is haywire on CloudKit. Maintaining a local cache that syncs with CloudKit is the best way I've found to make sure your data is accurate.

Answer 2

I'm 99% sure it was an iOS issue. After users updated to iOS 14.3 the problem disappeared