iCloud and Core Data - How to debug?

Question

I have an Library-style app which uses Core Data to store its data. Currently I am working on the integration of iCloud support.

I worked through several examples and the Apple docs and finally managed that an object created on device A is automatically synced to device B.

That is great but know I am experiencing the some problems: Some objects are synced and others are not and I have no idea how to debug this. Is there some way to "see" which data is transfered to iCloud, which data is stored in the cloud, and which data is downloaded from iCloud?

All I see at the moment is, that I create some NSManagedObject and store it to the ManagedContext/PersistentStore. I cannot see if it is transfered to the cloud and I cannot see the current content of the cloud. This makes it unpossible to debug the whole process.

So how to debug iCloud?

EDIT on 06/02/2015 I asked this question quite a while ago but it still gets some up votes or favorites. Therefore I would like to share some information I got meanwhile:

DO NOT USE iClOUD! I cannot tell you how many headacdhes and sleepless nights I had because of iCloud. It is jut not worth the candles. At least not when being used with Core Data. It just does not work reliably. This is even still true with iCloud Drive. My apps "supported" iCloud for about two years I did everything possible to get it running. Every time it seems to work I got new error messages from users. It worked fine for many users and caused trouble and even crashes for many othes. It was just terrible. Do your self a favour and use any other syncing service.

Answer 1

There seems to be a runtime argument

-com.apple.coredata.ubiquity.logLevel 3

check this article http://www.freelancemadscience.com/fmslabs_blog/2012/3/28/debug-settings-for-core-data-and-icloud.html ?

Answer 2

tried the mitmproxy to see what is send and what is received?

There is a GameCenter tutorial at http://mitmproxy.org/doc/tutorials/gamecenter.html , it should be similar for iClound transfers.