Swift 4 CloudKit queryCompletionBlock doesn't appear to execute

Question

I followed several CKQueryOperation examples/narratives on problems to fetch from CloudKit. My table has about 370 rows and 8 columns..at best I can only fetch about 60 rows. resultsLimit parameter does not seem to help.. My queryCompletionBlock is not executing. Sometimes I fetch 5 rows and other time 30+ Response from Cloud is quick just now all rows It's got to be some newbie code mistake!

func getData() {
    let predicate = NSPredicate(value: true)
    let query = CKQuery(recordType: RemoteFunctions.RemoteRecords.booksDB, predicate: predicate)
    let cloudContainer = CKContainer.default()
    let privateDatabase = cloudContainer.privateCloudDatabase
    let operation = CKQueryOperation(query: query)

    operation.queuePriority = .veryHigh
    operation.resultsLimit = 20

    operation.recordFetchedBlock = { (record: CKRecord) in
        self.allRecords.append(record)
         print(record)
    }
    operation.queryCompletionBlock = {[weak self] (cursor: CKQueryCursor?, error: NSError?) in
        // There is another batch of records to be fetched
        print("completion block called with \(String(describing: cursor))")

        if let cursor = cursor  {
            let newOperation = CKQueryOperation(cursor: cursor)
            newOperation.recordFetchedBlock = operation.recordFetchedBlock
            newOperation.queryCompletionBlock = operation.queryCompletionBlock
           newOperation.resultsLimit = 10
            privateDatabase.add(newOperation)
            print("more records")
        }
            // There was an error
        else if let error = error {
            print("Error:", error)
        }

            // No error and no cursor means the operation was successful
        else {
            print("Finished with records:")
        }
        } as? (CKQueryCursor?, Error?) -> Void

// privateDatabase.add(operation)

}

Answer 1

Remove the as? (CKQueryCursor?, Error?) -> Void near the end. Be careful not to remove the preceeding brace.

Remove newOperation.resultsLimit = 10 in your cursor block.

Add operation = newOperation immediately above privateDatabase.add(newOperation)

Uncomment the privateDatabase.add(operation)

That should help. Large fetches, where the cursor block gets hit more than 3 times can be problematic. If you do the above, you should be ok. Some people like to write/call the cursor block as its own function. That works as well, but it isn't necessary.

Answer 2

You could try this...

func getData(withCursor cursor: CKQueryCursor? = nil)
    {
    let cloudContainer = CKContainer.default()
    let privateDatabase = cloudContainer.privateCloudDatabase

    let operation: CKQueryOperation

    if let cursor = cursor
    {
        operation = CKQueryOperation(cursor: cursor)
    }
    else
    {
        let operation_configuration: CKOperationConfiguration = CKOperationConfiguration()
        operation_configuration.isLongLived = true
        operation_configuration.qualityOfService = .background

        let predicate = NSPredicate(value: true)
        let query = CKQuery(recordType: RemoteFunctions.RemoteRecords.booksDB, predicate: predicate)

        operation = CKQueryOperation(query: query)
        operation.queuePriority = .veryHigh
        operation.configuration = operation_configuration


        operation.recordFetchedBlock = { (record: CKRecord) in
            self.allRecords.append(record)
                print(record)
        }

        operation.queryCompletionBlock = {[weak self] (cursor: CKQueryCursor?, error: NSError?) in
            // There is another batch of records to be fetched
            print("completion block called with \(String(describing: cursor))")

            if let error = error 
            {
                print("Error:", error)
            }
            else if let cursor = cursor  
            {
                self.getData(withCursor: cursor)
            }
            else
            {
                print("Finished with records:")
            }
        }
    }

    privateDatabase.add(operation)
}

This is a recursive version of your fuction, using the new CKQueryOperation API.

It seems that your're loosing reference to the operation object when a cursor arrives.