Is there a possibility to infer the last time when the local core data store was completely synced to iCloud?

Question

I am wondering whether it is possible to determine at which time my local Core Data store was synchronized with iCloud. From iCloud is trivial. You can just take the time of the last NSPersistentStoreDidImportUbiquitousContentChangesNotification. However, I could not find any method to check when my local changes were completely transmitted to iCloud.

Any ideas?

Answer 1

You can't find this out. The only information available is the transaction logs, but those don't tell you when the data was actually synced. Transaction logs are created when you save changes. At some later time (probably soon, but there's no guarantee) they get synced to the iCloud service. You don't get notified of this.

It might be possible to infer sync timing via out-of-band communication from other devices. For example, when you receive the did-import notification, write the current time to NSUbiquitousKeyValueStore. Then monitor that key to see when changes are received at the other end. That would at least tell you that some changes had been received by some other device. At best though, it would notify you of when changes had been downloaded at the other end, not when they had been successfully uploaded to the iCloud service.