coredata intermittant crash [NSEntityDescription entityForName:inManagedObjectContext:]

Question

I have one customer using an iPad 2 that's experiencing a crash and I can't reproduce it.

Crash report:

Last Exception Backtrace:
0   CoreFoundation                  0x37a5429e __exceptionPreprocess
1   libobjc.A.dylib                 0x32b3b97a objc_exception_throw
2   CoreData                        0x317438d8 +[NSEntityDescription entityForName:inManagedObjectContext:]
3   MyApp                           0x000fc916 -[DetailViewController fetchedResultsController] (DetailViewController.m:237)
4   MyApp                           0x000fc374 -[DetailViewController addToMySermons] (DetailViewController.m:170)
5   MyApp                           0x000fc080 -[DetailViewController actionSheet:didDismissWithButtonIndex:] (DetailViewController.m:140)
6   UIKit                           0x35db60cc -[UIActionSheet(Private) _popoutAnimationDidStop:finished:]
7   UIKit                           0x35a73aae -[UIViewAnimationState sendDelegateAnimationDidStop:finished:]
8   UIKit                           0x35ae88ca -[UIViewAnimationState animationDidStop:finished:]
9   QuartzCore                      0x30a91bd4 CA::Layer::run_animation_callbacks(void*)
10  libdispatch.dylib               0x358924b2 _dispatch_client_callout
11  libdispatch.dylib               0x358971b8 _dispatch_main_queue_callback_4CF$VARIANT$mp
12  CoreFoundation                  0x37a27f36 __CFRunLoopRun
13  CoreFoundation                  0x3799aeb8 CFRunLoopRunSpecific
14  CoreFoundation                  0x3799ad44 CFRunLoopRunInMode
15  GraphicsServices                0x3989a2e6 GSEventRunModal
16  UIKit                           0x35ab22f4 UIApplicationMain
17  MyApp                           0x000f595a main (main.m:16)
18  MyApp                           0x000f5910 start + 36

I can see that it's happening at the +[NSEntityDescription entityForName:inManagedObjectContext:] call which looks like this:

NSEntityDescription *entity = [NSEntityDescription entityForName:@"StoredPage" inManagedObjectContext:self.managedObjectContext];

The self.managedObjectContext is passed in from UITableViewController on the left side of a UISplitViewController.

This works fine for me and the thousands of others using the app, it's only this one person thats having the problem. We've had him delete the app and reinstall it and reboot his iPad but it didn't help.

Is there a way for me to catch the actual exception thrown and display it in a UIAlertView so I can see what's actually happening or am I going to have to get his UDID and give him a debug version?

Answer 1

For me the issue was that the ManagedObjectContext did not have a persistent store coordinator.

To discover the details of the exception thrown I did the following

NSEntityDescription *entity = nil; @try { // do something entity = [NSEntityDescription entityForName:@"MyEntity" inManagedObjectContext:managedObjectContext]; } @catch (NSException *exception) { // error happened! do something about the error state NSLog(@"exception creating entity for managedobject content MyEntity = %@", exception); return nil; } @finally { // do something to keep the program still running properly }

Which logged the following:

```

exception creating entity for managedobject content MyEntity = +entityForName: nil is not a legal NSPersistentStoreCoordinator for searching for entity name 'MyEntity'

```

I appreciate this is an old question, but I suspect it's not that uncommon an issue.

Answer 2

Has your core data model changed?

I have seen some hard to reproduce and odd crashes occur when the Core Data model file doesn't match the one that was used at the time the database file was created.

This situation is best avoided by always creating a new "version" of your core data model (schema).