核心数据:解决奇怪的EXC_BAD_ACCESS错误

Question

我面临着一个非常奇怪的核心数据问题.我们来描述一下:

定义

假设我有两个模型,ModelA并且ModelB.在数据模型ModelA中引用ModelB为一对多关联,因此ModelB具有一对一的关联ModelA.

更新

当应用程序启动时(特别是在首次启动时),或者当用户询问时,我必须ModelB为每个ModelA实例创建或更新所有实例.ModelA实例是预先确定的 对于每个ModelA实例,我有大约200个实例ModelB.

我使用这样的代码:

ModelB *model = [NSEntityDescription insertNewObjectForEntityForName:@"ModelB"
                                              inManagedObjectContext:context];
model.value = [NSNumber numberWithDouble:myValue];
model.modelA = modelA; // I pass modelA as a parameter to the function
[modelA addModelBObject:model];

我不会立即保留数据(因为我有很多数据要保存),但我在流程结束时这样做.

错误

有时,有时候,我EXC_BAD_ACCESS在这一行得到一个错误:

model.value = [NSNumber numberWithDouble:myValue];

启用僵尸,我不能只看到那些愚蠢的EXC_BAD_ACCESS,没有更多的信息.

真奇怪的错误

我尝试以不同的方式设置该值,但没有任何改变.然后,我尝试retain了NSNumber,但没有改变.然后,最后,我尝试retain了一旦创建的模型,我得到了平常EXC_BAD_ACCESS,但相应地创建了模型,也就是说:

ModelB *model = [[NSEntityDescription insertNewObjectForEntityForName:@"ModelB"
                                               inManagedObjectContext:context] retain];

想法？

您对如何解决此问题有任何想法吗？难道我做错了什么？顺便说一句,如果我减慢了很多东西(比如每次创建新模型时保存上下文),这个问题显然不会发生,但这确实会减慢整个应用程序的速度......

编辑

在一些罕见的情况下,我得到这个堆栈跟踪:

Serious application error.  Exception was caught during Core Data change processing.  This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.  -[__NSCFSet addObject:]: attempt to insert nil with userInfo (null)
2011-06-15 11:36:59.864 myApp[457:607] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFSet addObject:]: attempt to insert nil'
*** Call stack at first throw:
(
0   CoreFoundation                      0x313dc64f __exceptionPreprocess + 114
1   libobjc.A.dylib                     0x34b3dc5d objc_exception_throw + 24
2   CoreFoundation                      0x313dc491 +[NSException raise:format:arguments:] + 68
3   CoreFoundation                      0x313dc4cb +[NSException raise:format:] + 34
4   CoreFoundation                      0x31351089 -[__NSCFSet addObject:] + 152
5   CoreData                            0x35136dd9 -[NSManagedObjectContext(_NSInternalChangeProcessing) _processPendingUpdates:] + 524
6   CoreData                            0x350f4b3d -[NSManagedObjectContext(_NSInternalChangeProcessing) _processRecentChanges:] + 724
7   CoreData                            0x351363a5 -[NSManagedObjectContext processPendingChanges] + 16
8   CoreData                            0x350d027f _performRunLoopAction + 126
9   CoreFoundation                      0x313b3a35 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 16
10  CoreFoundation                      0x313b5465 __CFRunLoopDoObservers + 412
11  CoreFoundation                      0x313b675b __CFRunLoopRun + 854
12  CoreFoundation                      0x31346ec3 CFRunLoopRunSpecific + 230
13  CoreFoundation                      0x31346dcb CFRunLoopRunInMode + 58
14  GraphicsServices                    0x3658841f GSEventRunModal + 114
15  GraphicsServices                    0x365884cb GSEventRun + 62
16  UIKit                               0x368ded69 -[UIApplication _run] + 404
17  UIKit                               0x368dc807 UIApplicationMain + 670
18  myApp                               0x000028cf main + 82
19  myApp                               0x00002878 start + 40
)
terminate called after throwing an instance of 'NSException'

编辑2

这是异常的堆栈跟踪:

#0  0x313f1460 in __CFBasicHashAddValue ()
#1  0x3133fff8 in CFBasicHashAddValue ()
#2  0x31344162 in CFSetAddValue ()
#3  0x31351012 in -[__NSCFSet addObject:] ()
#4  0x3514211a in _PFFastMOCObjectWillChange ()
#5  0x3512ed46 in _PF_ManagedObject_WillChangeValueForKeyIndex ()
#6  0x35132e7e in _sharedIMPL_setvfk_core ()
#7  0x3513316a in _svfk_2 ()
#8  0x0003b750 in -[_TassoStorico setValoreValue:] (self=0x6d97bf0, _cmd=0x49064, value_=1.02600002) at _TassoStorico.m:87
#9  0x0001b62e in -[EuriborParser(hidden) readStoricoForzato] (self=0x74200d0, _cmd=0x48ff7) at EuriborParser.m:236
#10 0x31349f02 in -[NSObject(NSObject) performSelector:withObject:] ()
#11 0x000441c4 in -[MBProgressHUD launchExecution] (self=0x90a6ff0, _cmd=0x4b83f) at MBProgressHUD.m:482
#12 0x352b3388 in -[NSThread main] ()
#13 0x353255cc in __NSThread__main__ ()
#14 0x34e20310 in _pthread_start ()
#15 0x34e21bbc in thread_start ()

Answer 1

CoreData不是线程安全的; 看起来这是你的问题尝试看这个问题

Answer 2

我有一个类似的问题([managedContext save]上的EA_BAD_ACCESS),这是由KeyValueObserver引起的,当它本来应该没有删除时.追踪非常困难.这意味着即使使用ARC,我也会遇到这种行为.