Swift iOS EKEventStore：从EKEvent获取参加者有时会与NSInvalid

var allCals = _eventStore.calendarsForEntityType(EKEntityTypeEvent)

var predicate:NSPredicate! = _eventStore.predicateForEventsWithStartDate(yearsAgo,endDate:toAgo,calendars:allCals)

_eventStore.enumerateEventsMatchingPredicate(predicate,usingBlock:{
            (event:EKEvent!,stop:UnsafeMutablePointer<ObjCBool>) in

            if (event.title != nil
                && event.calendar != nil
                && event.calendar.calendarIdentifier != nil
                && event.lastModifiedDate != nil
                ){

                        if event.attendees != nil{ // < -- SOMETIMES LEADS TO CRASH!!
                            //...
                        }
                        else{ // standalone
                             //...
                        }
         }

   //......
 })// end block

完整堆栈跟踪：[线程崩溃异常]

Thread : Fatal Exception: NSInvalidArgumentException
0  CoreFoundation                 0x2917649f __exceptionPreprocess + 126
1  libobjc.A.dylib                0x36970c8b objc_exception_throw + 38
2  CoreFoundation                 0x29096291 -[__NSSetM addObject:] + 608
3  EventKit                       0x29b4eacf -[EKPersistentObject primitiveRelationValueForKey:] + 502
4  Foundation                     0x29dc1617 -[NSObject(NSKeyValueCoding) valueForKey:] + 202
5  EventKit                       0x29b5afc5 -[EKObjectToManyRelation _loadedItems] + 120
6  EventKit                       0x29b5aef3 -[EKObjectToManyRelation _effectiveItems] + 102
7  EventKit                       0x29b5ae69 -[EKObjectToManyRelation items] + 20
8  EventKit                       0x29b5d179 -[EKCalendarItem attendees] + 36
9  MyApp                       0x000d8c78 _TTSf2n_n_n_n_n_d_i_n_n___TFFC8MyApp17WmBuildGroupsTask14doInBackgroundFS0_FT_T_U_FTGSqCSo7EKEvent_GVSs20UnsafeMutablePointerV10ObjectiveC8ObjCBool__T_ (WmBuildGroupsTask.swift:421)
10 MyApp                       0x000d3f3c _TPA__TTSf2n_n_n_n_n_d_i_n_n___TFFC8MyApp17WmBuildGroupsTask14doInBackgroundFS0_FT_T_U_FTGSqCSo7EKEvent_GVSs20UnsafeMutablePointerV10ObjectiveC8ObjCBool__T_ (WmBuildGroupsTask.swift)
11 MyApp                       0x000d96b8 reabstraction thunk helper from @callee_owned (@owned Swift.ImplicitlyUnwrappedOptional<ObjectiveC.EKEvent>,@unowned Swift.UnsafeMutablePointer<ObjectiveC.ObjCBool>) -> (@unowned ()) to @callee_unowned @objc_block (@unowned Swift.ImplicitlyUnwrappedOptional<ObjectiveC.EKEvent>,@unowned Swift.UnsafeMutablePointer<ObjectiveC.ObjCBool>) -> (@unowned ()) (WmBuildGroupsTask.swift)
12 EventKit                       0x29ba72a7 __60-[EKEventStore enumerateEventsMatchingPredicate:usingBlock:]_block_invoke + 130
13 EventKit                       0x29bad6af __41-[EKPredicateSearch startWithCompletion:]_block_invoke_2 + 690
14 libdispatch.dylib              0x36ed07bb _dispatch_call_block_and_release + 10
15 libdispatch.dylib              0x36ed9dab _dispatch_root_queue_drain + 866
16 libdispatch.dylib              0x36edacd7 _dispatch_worker_thread3 + 94
17 libsystem_pthread.dylib        0x37031e31 _pthread_wqthread + 668
18 libsystem_pthread.dylib        0x37031b84 start_wqthread + 8

Thread : Crashed: com.apple.root.default-qos
0  libsystem_kernel.dylib         0x36fb6dfc __pthread_kill + 8
1  libsystem_pthread.dylib        0x37034d37 pthread_kill + 62
2  libsystem_c.dylib              0x36f56909 abort + 76
3  libc++abi.dylib                0x362919c9 __cxa_bad_cast
4  libc++abi.dylib                0x362ab671 default_unexpected_handler()
5  libobjc.A.dylib                0x36970f25 _objc_terminate() + 192
6  libc++abi.dylib                0x362a8de3 std::__terminate(void (*)()) + 78
7  libc++abi.dylib                0x362a85a9 __cxxabiv1::exception_cleanup_func(_Unwind_Reason_Code,_Unwind_Exception*)
8  libobjc.A.dylib                0x36970d5f objc_exception_throw + 250
9  CoreFoundation                 0x29096291 -[__NSSetM addObject:] + 608
10 EventKit                       0x29b4eacf -[EKPersistentObject primitiveRelationValueForKey:] + 502
11 Foundation                     0x29dc1617 -[NSObject(NSKeyValueCoding) valueForKey:] + 202
12 EventKit                       0x29b5afc5 -[EKObjectToManyRelation _loadedItems] + 120
13 EventKit                       0x29b5aef3 -[EKObjectToManyRelation _effectiveItems] + 102
14 EventKit                       0x29b5ae69 -[EKObjectToManyRelation items] + 20
15 EventKit                       0x29b5d179 -[EKCalendarItem attendees] + 36
16 MyApp                       0x000d8c78 _TTSf2n_n_n_n_n_d_i_n_n___TFFC8MyApp17WmBuildGroupsTask14doInBackgroundFS0_FT_T_U_FTGSqCSo7EKEvent_GVSs20UnsafeMutablePointerV10ObjectiveC8ObjCBool__T_ (WmBuildGroupsTask.swift:421)
17 MyApp                       0x000d3f3c _TPA__TTSf2n_n_n_n_n_d_i_n_n___TFFC8MyApp17WmBuildGroupsTask14doInBackgroundFS0_FT_T_U_FTGSqCSo7EKEvent_GVSs20UnsafeMutablePointerV10ObjectiveC8ObjCBool__T_ (WmBuildGroupsTask.swift)
18 MyApp                       0x000d96b8 reabstraction thunk helper from @callee_owned (@owned Swift.ImplicitlyUnwrappedOptional<ObjectiveC.EKEvent>,@unowned Swift.UnsafeMutablePointer<ObjectiveC.ObjCBool>) -> (@unowned ()) (WmBuildGroupsTask.swift)
19 EventKit                       0x29ba72a7 __60-[EKEventStore enumerateEventsMatchingPredicate:usingBlock:]_block_invoke + 130
20 EventKit                       0x29bad6af __41-[EKPredicateSearch startWithCompletion:]_block_invoke_2 + 690
21 libdispatch.dylib              0x36ed07bb _dispatch_call_block_and_release + 10
22 libdispatch.dylib              0x36ed9dab _dispatch_root_queue_drain + 866
23 libdispatch.dylib              0x36edacd7 _dispatch_worker_thread3 + 94
24 libsystem_pthread.dylib        0x37031e31 _pthread_wqthread + 668

第9行a.e. WmBuildGroupsTask.swift：421如果event.attendees！= nil {

任何人都可以散布如何摆脱这场崩溃，或至少使代码安全从崩溃？

[编辑1]

我也试过：

if event.hasAttendees {

  if let attArray:NSArray = event.attendees{ // crashes here

    /* ... */
  }

}}

有趣的是，从命令行：po event.hasAttendees返回true

当po event.attendees返回null时。但还是崩溃了

[编辑2]

升级到Swift 1.2后，得到同样的崩溃(Crashlytics)。还试过：

if event.hasAttendees {

  if let attArray:[EKParticipant] = event.attendees as? [EKParticipant] // crash here
 {
    /* ... */
  }                      
}

有问题的事件是指像Google这样的日历，正如我上面提到的一样，99.5％的同一事件正常工作，并且我取得了与会者的成功。

我不是iOS大师，但看起来像它的内部iOS问题：

libobjc.A.dylib                0x36970d5f objc_exception_throw + 250
9  CoreFoundation                 0x29096291 -[__NSSetM addObject:] + 608
10 EventKit                       0x29b4eacf -[EKPersistentObject primitiveRelationValueForKey:] + 502
11 Foundation                     0x29dc1617 -[NSObject(NSKeyValueCoding) valueForKey:] + 202
12 EventKit                       0x29b5afc5 -[EKObjectToManyRelation _loadedItems] + 120
13 EventKit                       0x29b5aef3 -[EKObjectToManyRelation _effectiveItems] + 102
14 EventKit                       0x29b5ae69 -[EKObjectToManyRelation items] + 20
15 EventKit                       0x29b5d179 -[EKCalendarItem attendees] + 36

谢谢，