Database Reference
In-Depth Information
Figure 18—Turning on iCloud debugging
The logs can also help us watch for corruption, which appears to occur most
frequently during development. Without logging's early warning system, cor-
ruption can be quite frustrating when it happens. Without the aid of logging,
things just stop. No errors are generated; iCloud just stops working. With
logging turned on, we can glean when something goes wrong.
Unfortunately, at this time, there is no way to determine at runtime, within
our application, that corruption has occurred.
Further, once a log file has been corrupted, there is no way to clear it out.
The best that we can do is to start over with a new file.
This is currently being tracked under
rdar://10837238
.
Transaction Logs
iCloud functions through transaction logs. Similar to how modern version
control systems work, every time a save is performed by an “iCloud-backed”
persistent store, a transaction log is created that details what happened in
that save. These transaction logs are kept in order and pushed up to the
cloud. On other devices, the transaction logs are received and played back
