问题
I have an Mac Application using a NSPersistentDocument. I want to get notified when Objects are deleted to save this information using Core Data. So I'm listening for NSManagedObjectContextObjectsDidChangeNotification. Often it is called instantly when objects are deleted, but sometimes it is only called after the persistent document is saved with all deleted objects not being notified before. Because I want to let the user directly export all existing objects (and not the deleted anymore) what to I have to do to become notified instantly to save the delete information or do I have to use it in another way?
回答1:
NSManagedObjectContextObjectsDidChangeNotification is no longer issued as frequently or quickly on 10.7 as on 10.6. You can force Core Data to issue the notification (assuming there are changes) by calling -[NSManagedObjectContext processPendingChanges].
来源：https://stackoverflow.com/questions/7742308/nsmanagedobjectcontextobjectsdidchangenotification-not-always-called-instantly