CKFetchRecordZoneChangesOperation - recordZoneChangeTokensUpdatedBlock

Question

Hi

I have CKFetchRecordZoneChangesOperation with a recordZoneChangeTokensUpdatedBlock

recordZoneChangeTokensUpdatedBlock is getting called multiple times.

Inside recordZoneChangeTokensUpdatedBlock, I try to save the records that are received upto that point in time (collected from recordChangedBlock) and save the server change token so that if the operation fails at a later point, re-creating another CKFetchRecordZoneChangesOperation could use the server change token that was cached and need not fetch from scratch.

References:

This approach was explained in

https://developer.apple.com/library/content/documentation/DataManagement/Conceptual/CloudKitQuickStart/MaintainingaLocalCacheofCloudKitRecords/MaintainingaLocalCacheofCloudKitRecords.html

What's New with CloudKit

Problem:

The records received upto that point are not in order.

For example:

I have a master and transaction record types.

I receive 5 transaction records without a single master record.

So when I try to save them the records are in an inconsistent state for the app to function.

Note:

When I saved the records, I saved master and transactions records in a single operation and was saved successfully (using CKModifyRecordsOperation)

Workaround:

I can use the fetchRecordZoneChangesCompletionBlock to save the records into the local cache (Core Data), but for a large operation which fetches a lot of changes with multiple change tokens the user has to wait till the operation completes (as opposed to seeing batches of changes)

My Understanding:

- Based on the video and the documentation, I thought the recordChangedBlock would be called sequentially so that in the recordZoneChangeTokensUpdatedBlock we can save the records changes that have accumulated so far and be in a consistent state.

I really hope someone can help me on this as this. Thanks.

927

Posted by

newwbee

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Answer 1

It's a database and the results come back unsorted unless you add a sortDescriptor and do a query based search:

https://developer.apple.com/documentation/cloudkit/ckquery/1413121-sortdescriptors?language=objc

I accumulate all the results and do my own sort

tableRowData = [data sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
        NSDate *first = [a objectForKey:@"TimeStamp"];
        NSDate *second =[b objectForKey:@"TimeStamp"];
        return [second compare:first];
    }];

Posted by

PBK

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CKFetchRecordZoneChangesOperation - recordZoneChangeTokensUpdatedBlock

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