当我调用[NSManagedObject save]方法时，我遇到了异常。
这是一个IM应用程序。应用程序同步历史消息时引发此异常。我有很多离线消息。我用来为每条消息打电话[NSManagedContext save]。我想这次崩溃的原因是保存方法调用的频率太快了。
回溯：
Last Exception Backtrace:
0 CoreFoundation 0x21f70c1f __exceptionPreprocess + 127
1 libobjc.A.dylib 0x2f9e9c8b objc_exception_throw + 38
2 CoreData 0x21d38b6b -[NSSQLCore recordChangeSnapshot:forObjectID:] + 206
3 CoreData 0x21cac8f5 -[NSSQLCore prepareForSave:] + 656
4 CoreData 0x21cabd6f -[NSSQLCore saveChanges:] + 626
5 CoreData 0x21c7a93d -[NSSQLCore executeRequest:withContext:error:] + 736
6 CoreData 0x21d275c5 __65-[NSPersistentStoreCoordinator executeRequest:withContext:error:]_block_invoke + 3564
7 CoreData 0x21d2e76b gutsOfBlockToNSPersistentStoreCoordinatorPerform + 262
8 libdispatch.dylib 0x2ff497a7 _dispatch_client_callout + 22
9 libdispatch.dylib 0x2ff50ac9 _dispatch_barrier_sync_f_invoke + 48
10 CoreData 0x21d222a7 _perform + 134
11 CoreData 0x21c7a517 -[NSPersistentStoreCoordinator executeRequest:withContext:error:] + 314
12 CoreData 0x21c9bf75 -[NSManagedObjectContext save:] + 856
13 MTMessage 0x000a4111 __50-[XMPPMessageModule xmppStream:didReceiveMessage:]_block_invoke180 (XMPPMessage.m:227)
14 CoreData 0x21cff74d developerSubmittedBlockToNSManagedObjectContextPerform + 180
15 libdispatch.dylib 0x2ff515b1 _dispatch_queue_drain + 952
16 libdispatch.dylib 0x2ff4bf85 _dispatch_queue_invoke + 84
17 libdispatch.dylib 0x2ff52b9b _dispatch_root_queue_drain + 338
18 libdispatch.dylib 0x2ff53cd7 _dispatch_worker_thread3 + 94
19 libsystem_pthread.dylib 0x300aae31 _pthread_wqthread + 668
20 libsystem_pthread.dylib 0x300aab84 start_wqthread + 8