CKModifyRecordsOperation - create referenced records simultaneously? - swift

Question

I'm working to refactor a somewhat clunky iterative save loop for CloudKit to use CKModifyRecordsOperation and bulk save records.
I have a Course, which has 1+ Weeks, each which has 1+ Lessons. Previously I'd create the Course in CloudKit, then create the Weeks, then the Lessons and circle back to update the Weeks with the Lesson references once created. And also fetch and save the Course record with the references to the Weeks once Weeks were created.
I've refactored to create all (Course, Week and Lesson) records locally, with the relevant references set up. E.g., course["weeks"] contains the record references for each week I've created locally, for example:
course["weeks"] = getWeekRefsForCourse(for: allWeeks)
func getWeekRefsForCourse(for allWeeks: [CKRecord]) -> [CKRecord.Reference] {
var weekRefsArray: [CKRecord.Reference] = []
for each in allWeeks {
let weekRef = CKRecord.Reference(record: each, action: .deleteSelf)
weekRefsArray.append(weekRef)
return weekRefsArray
}
The issue is when I go to save, the error I get back is:
Invalid list of records: Cycle detected in record graph
This suggests that I've got a record referring to itself, but I've gone record by record and I I can't see anything. The Weeks reference the Course and the Lessons, but not themselves, etc. So my only theory is that because I'm trying to save items that refer to other items that haven't yet been created, what I'm trying to do isn't possible.
Is the correct protocol here actually my original approach? Or is there something I'm missing?
Original approach:
Save Course
Save Week
Save Lessons
Update Weeks with Lesson references
Update Course with Week references
CKModifyRecordsOperation code:
let bulkSaveQueryOp = CKModifyRecordsOperation()
bulkSaveQueryOp.recordsToSave = [courseRecord]
bulkSaveQueryOp.recordsToSave?.append(contentsOf: weeks)
bulkSaveQueryOp.recordsToSave?.append(contentsOf: lessons)
//note I've confirmed I have the correct number of records
bulkSaveQueryOp.modifyRecordsCompletionBlock = { records, recordIDs, error in
if let error = error as? CKError {
log.error(error)
} else { // success }
}
CKContainer.default().publicCloudDatabase.add(bulkSaveQueryOp)

Answer 1

I'm fairly certain you can create all these records together. I suspect there must be something else wrong and that's why you are getting that error.
You can create a CKReference to an object that doesn't even exist and CloudKit will still create it. A CKReference is little more than a pointer to a recordName of another object in the container.
Combining all those records into a CKModifyRecordsOperation is the right thing to do and you shouldn't have to be careful about the order of your CKRecord saves. I think another issue must be lurking somewhere.

Answer 2

I was able to find a similar question over in the apple dev forums for someone that had a similar issue and and it helped identify the source of the problem - that I had effectively created a loop with my .deleteSelf actions I was creating on various references.
So while the references were fine, the actions were what was causing the error.
Once I double checked and adjusted those, the error went away and I was able to save.
Spotting this was made more complex by the fact that I wasn't changing the .deleteSelf actions version what I had previously done - and was working fine - when my saves were done in sequence rather than a bulk CKModifyRecordsOperation save.
So it seams that another added benefit of CKModifyRecordsOperation with a bulk save is that it adds a layer of stupidity checking that creating items individually doesn't :)