CKQueryOperation queryCompletionBlock 返回零 cursor

Question

I'm fetching a CloudKit database with CKQueryOperation. For some reason every time when I press a fetch button, the first time I get a nil cursor. The second time it fetches and gets data, it's all good. When I check the recordFetchedBlock it does get the results and appends them, but at the end the array is empty. I don't understand why this happens. I want to show the results immediately since they have been fetched. I think the problem is with the nil cursor, but I'm open for other suggestions. Here's my code:

public class CloudKitDatabase {

static let shared = CloudKitDatabase()

var records = [CKRecord]()

let publicData = CKContainer.default().publicCloudDatabase

init() {
    self.fetchRecords()
}

func fetchRecords() {

    let predicate = NSPredicate(value: true)
    let query = CKQuery(recordType: "OECD", predicate: predicate)

    let queryOperation = CKQueryOperation(query: query)

    queryOperation.recordFetchedBlock = {
        record in
        self.records.append(record)


    }

    queryOperation.queryCompletionBlock = { cursor, error in
        DispatchQueue.main.async {
            if error != nil {
                print(error.debugDescription)
            } else {
                if cursor != nil {
                    self.queryServer(cursor!)
                } else {
                    print("CURSOR IS NIL")
                }
            }
        }

    }
    self.publicData.add(queryOperation)
}


func queryServer(_ cursor: CKQueryOperation.Cursor) {
    let queryOperation = CKQueryOperation(cursor: cursor)

    queryOperation.recordFetchedBlock = {
        record in
        self.records.append(record)

    }

    queryOperation.queryCompletionBlock = { cursor, error in
        DispatchQueue.main.async {
            if error != nil {
                print(error.debugDescription)
            } else {
                if cursor != nil {
                    self.queryServer(cursor!)
                } else {
                    print("CURSOR IS NIL")
                }
            }
        }
    }
    self.publicData.add(queryOperation)

}

The Debug area tells me that: CURSOR IS NIL and CloudKitDatabase.shared.records.isEmpty is true

Answer 1

First try some configs on the first query;

   let queryOperation = CKQueryOperation(query: query)
   queryOperation.queuePriority = .veryHigh
   queryOperation.resultsLimit = 99 // built in limit is 400  

Next, don't do the cursor calls in a dispatch and include your completions;

queryOperation.queryCompletionBlock =
{ cursor, error in

        if error != nil {
            print(error.debugDescription)
        } else {
            if cursor != nil {
                self.queryServer(cursor!)
            } else {
                print("CURSOR IS NIL")
                completion(nil)
            }
        }
}

and;

queryOperation.queryCompletionBlock = 
{ cursor, error in

        if error != nil {
            print(error.debugDescription)
        } else {
            if cursor != nil {
                self.queryServer(cursor!)
            } else {
                print("CURSOR IS NIL")
                completion(nil)
            }
        }

}

also don't forget to empty your records array at the beginning of fetchRecords otherwise successive calls will get the same records in the array.