在两个实体之间执行排序

Question

我有一个实体EventScheduleOnc，其属性eventNameOnc与EventDec实体具有一对一关系，属性为eventStatus。我正在尝试执行这样的排序

 var fetchedResultsController: NSFetchedResultsController = { () -> NSFetchedResultsController<NSFetchRequestResult> in 

    let eventsOncFetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName:"EventScheduleOnc")
    let primarySortDescriptor = NSSortDescriptor(key:"EventDec.eventStatus", ascending: true)
    let secondarySortDescriptor = NSSortDescriptor(key:"eventNameOnc", ascending: true)
    eventsOncFetchRequest.sortDescriptors = [primarySortDescriptor,secondarySortDescriptor]

    let frc = NSFetchedResultsController(fetchRequest: eventsOncFetchRequest, managedObjectContext:context,
                                         sectionNameKeyPath:"EventDec.eventStatus",cacheName: nil)
    frc.delegate = self

    return frc}()

我收到此错误

  

***因未捕获的异常而终止应用   ＆＃39; NSInvalidArgumentException＆＃39;，原因：＆＃39; keypath EventDec.eventStatus   在实体＆＃39;

中找不到