我正在使用MagicalRecord为表创建一个NSFetchedResultsController。我有包含人群的NSManagedObjects，这里有两个例子:ContactGroup*everyoneContactGroup=[ContactGroupfindFirstByAttribute:@"groupId"withValue:@""];if(!everyoneContactGroup){everyoneContactGroup=[ContactGroupcreateEntity];[everyoneContactGroupsetGroupId:@""];[everyone