error with Core Data and iCloud - ios

Question

I am trying to work with Core Data and iCloud.
It worked once and it did not again.
I got this error below :
2015-05-19 12:11:13.695 Student Notebook App[34617:992535] -[Student_Notebook_App.NotebookTableView persistentStoreWillChange]: unrecognized selector sent to instance 0x7f86495514b0
2015-05-19 12:11:13.737 Student Notebook App[34617:992535] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Student_Notebook_App.NotebookTableView persistentStoreWillChange]: unrecognized selector sent to instance 0x7f86495514b0'
*** First throw call stack:
(
0 CoreFoundation 0x0000000110638c65 __exceptionPreprocess + 165
1 libobjc.A.dylib 0x000000010ff15bb7 objc_exception_throw + 45
2 CoreFoundation 0x00000001106400ad -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
3 CoreFoundation 0x000000011059613c ___forwarding___ + 988
4 CoreFoundation 0x0000000110595cd8 _CF_forwarding_prep_0 + 120
5 CoreFoundation 0x000000011060854c __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 12
6 CoreFoundation 0x0000000110506a04 _CFXNotificationPost + 2484
7 Foundation 0x000000010fa6c968 -[NSNotificationCenter postNotificationName:object:userInfo:] + 66
8 CoreData 0x0000000110303d5b __81-[PFUbiquitySetupAssistant tryToReplaceLocalStore:withStoreSideLoadedByImporter:]_block_invoke + 283
9 libdispatch.dylib 0x00000001131f5614 _dispatch_client_callout + 8
10 libdispatch.dylib 0x00000001131e02fa _dispatch_barrier_sync_f_slow_invoke + 275
11 libdispatch.dylib 0x00000001131f5614 _dispatch_client_callout + 8
12 libdispatch.dylib 0x00000001131dda1c _dispatch_main_queue_callback_4CF + 1664
13 CoreFoundation 0x00000001105a01f9 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
14 CoreFoundation 0x0000000110561dcb __CFRunLoopRun + 2043
15 CoreFoundation 0x0000000110561366 CFRunLoopRunSpecific + 470
16 GraphicsServices 0x0000000114e91a3e GSEventRunModal + 161
17 UIKit 0x0000000110c73900 UIApplicationMain + 1282
18 Student Notebook App 0x000000010f923aa7 main + 135
19 libdyld.dylib 0x0000000113229145 start + 1
20 ??? 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
Please, anyone can help me??
Thanks in Advance

Answer 1

The error is pretty clear:
-[Student_Notebook_App.NotebookTableView persistentStoreWillChange]: unrecognized selector sent to instance 0x7f86495514b0
This says that your code is trying to call a method named persistentStoreWillChange on a class that doesn't have that method.
The stack trace indicates that this happened when a notification was posted. It doesn't say which one. What happened is:
You registered to observe a notification with a method named persistentStoreWillChange.
Later that notification was posted. The notification system tried to call persistentStoreWillChange, but the method did not exist.
When you register for a notification, the callback method name that you provide must exist.