CloudKitRepository+queryUpdates.swift

func queryUpdates (sinceDate: Date, completion: @escaping ([Task], [String], NSError?) -> Void) {
        
        let changeToken = UserDefaults.standard.serverChangeToken
        
        fetchChangedRecords(token: changeToken, 
                            previousRecords: [], 
                            previousDeletedRecordsIds: [], 
                            completion: { (changedRecords, deletedRecordsIds) in
                                
            completion(self.tasksFromCKTasks(changedRecords), self.idsFromCKRecordIds(deletedRecordsIds), nil)
        })
}

func fetchChangedRecords (token: CKServerChangeToken?, 
                              previousRecords: [CKRecord], 
                              previousDeletedRecordsIds: [CKRecordID], 
                              completion: @escaping ((_ changedRecords: [CKRecord], _ deletedRecordsIds: [CKRecordID]) -> Void)) {
        
        var changedRecords = previousRecords
        var deletedRecordsIds = previousDeletedRecordsIds
        
        let op = CKFetchRecordChangesOperation(recordZoneID: customZone.zoneID, previousServerChangeToken: token)
        
        op.recordChangedBlock = { record in
            changedRecords.append(record)
        }
        op.recordWithIDWasDeletedBlock = { recordID in
            deletedRecordsIds.append(recordID)
        }
        op.fetchRecordChangesCompletionBlock = { serverChangeToken, data, error in
            
            guard error == nil else {
                completion(changedRecords, deletedRecordsIds)
                return
            }
            UserDefaults.standard.serverChangeToken = serverChangeToken
            
            if op.moreComing {
                self.fetchChangedRecords(token: serverChangeToken, 
                                         previousRecords: changedRecords, 
                                         previousDeletedRecordsIds: deletedRecordsIds, 
                                         completion: completion)
            } else {
                completion(changedRecords, deletedRecordsIds)
            }
        }
        privateDB.add(op)
    }