Core Data unresolved error on save - iphone

Question

I'm getting an error when saving my core data context, here is the log:
Unresolved error Error Domain=NSCocoaErrorDomain Code=134030 "The operation couldn’t be completed. (Cocoa error 134030.)" UserInfo=0x1937a0 {NSAffectedStoresErrorKey=(
"<NSSQLCore: 0x156410>"
), NSUnderlyingError=0x181a60 "The operation couldn’t be completed. (Cocoa error 4.)", NSFilePath=/var/mobile/Applications/appid/Documents/appname.sqlite}, {
NSAffectedStoresErrorKey = (
"<NSSQLCore: 0x156410>"
);
NSFilePath = "/var/mobile/Applications/appid/Documents/appname.sqlite";
NSUnderlyingError = "Error Domain=NSCocoaErrorDomain Code=4 \"The operation couldn\U2019t be completed. (Cocoa error 4.)\" UserInfo=0x181a30 {NSUnderlyingError=0x108ab0 \"The operation couldn\U2019t be completed. No such file or directory\"}";
}
I receive this error after removing and deleting an object:
[productList removeMProductObject:product];
[[delegate managedObjectContext] deleteObject:product];
[delegate saveContext];
I also noted that i also receive the error for the following scenarios(debugging):
1.
[productList removeMProductObject:product];
[delegate saveContext];
2.
[[delegate managedObjectContext] deleteObject:product];
[delegate saveContext];
3.
[[delegate managedObjectContext] deleteObject:product];
[productList removeMProductObject:product];
[delegate saveContext];
4.
[[delegate managedObjectContext] deleteObject:product];
[delegate saveContext];//error
[productList removeMProductObject:product];
[delegate saveContext];
5.
[productList removeMProductObject:product];
[delegate saveContext];//error
[[delegate managedObjectContext] deleteObject:product];
[delegate saveContext];
At times, i may pass around either the productList or a product object (both of type NSManagedObject) to other controllers, always using assign in the property and never retain. productList is an object which may contain many product objects.
I am able to create new objects(NSManagedObject), but when it comes to deleting them i get the error mentioned above. When running the application in the simulator i keep a close eye on the sqlite file. after attempting to delete an object(code above), i notice the .sqlite file is removed.
I have created a few Core Data iphone applications with no problem but i seem to be having an issue here. i don't believe i am doing anything out of the ordinary but perhaps i am missing a small detail, but i don't know what!
Why is my .sqlite file being deleted and resulting in this error message on save?
How can i find a more useful error message so i can determine the cause of this error?

Answer 1

Found the problem, but i'm not sure why it fixes it:
Before i would delete/remove the object i would delete the image associated with it(stored in the document's directory).
The image by default has no value(nil), but i would attempt to delete it anyway:
NSError *deleteError = nil;
[[NSFileManager defaultManager] removeItemAtPath:[DOCUMENTS_DIRECTORY stringByAppendingPathComponent:product.mPictureName] error:&deleteError];
#ifdef DEBUG_MODE
if(deleteError) {
NSLog(#"Error deleting image: %#", [deleteError description]);
}
else {
NSLog(#"Image %# deleted.", product.mPictureName);
}
#endif
if i instead do a nil check before attempting to remove the image like this, i get no error when i delete the managed object itself:
NSString *imageName = product.mPictureName;
if(imageName) {
NSError *deleteError = nil;
[[NSFileManager defaultManager] removeItemAtPath:[DOCUMENTS_DIRECTORY stringByAppendingPathComponent:imageName] error:&deleteError];
#ifdef DEBUG_MODE
if(deleteError) {
NSLog(#"Error deleting image: %#", [deleteError description]);
}
else {
NSLog(#"Image %# deleted.", imageName);
}
#endif
}
...
//delete NSManagedObject and save
i guess attempting to access the product's picture when it is nil makes it all invalid.

Answer 2

I had a similar issue that's worth reporting for any poor shmo that gets caught up in this issue. In my case I had a table view controller that handled row deletions by deleting the corresponding data from the data model. When I used the remove##ObjectName##Object method (stubbed out by the auto-generated NSManagedObject subclass), I would get an error similar to the one you reported.
When I instead used NSManagedObjectContext: deleteObject I didn't have a problem saving the context. But, I observed an exception being thrown with no indication of reason from the console.
It turns out the tableView method canEditRowAtIndexPath: was being called for the row corresponding to the newly deleted object. It was clear my row count needed to be updated prior to the OS calling this method. But, I don't care. I simply check to see whether the size of my array of managed objects can be indexed by the indexPath row.
if([managedObjSet.objects count] > indexPath.row) {
ManagedObject* obj = [managedObjectArray objectAtIndex:indexPath.row];
return ([obj.anotherManagedObjSet count] ==0);
}