当我使用NSPersistentStoreUbiquitousContentNameKey和NSPersistentStoreUbiquitousContentURLKey添加持久性存储时，我的应用程序每隔一秒就会崩溃并出现异常。这在调用addPersistentStoreWithType:configuration:URL:options:error:
堆栈跟踪如下所示：
*** Terminating app due to uncaught exception 'NSInvalidArgumentException',
reason: 'An NSManagedObject of class 'PFUbiquityPeer' must have a valid
NSEntityDescription.'
*** First throw call stack:
(
0 CoreFoundation 0x00007fff8b35ffc6 __exceptionPreprocess + 198
1 libobjc.A.dylib 0x00007fff83368d5e objc_exception_throw + 43
2 CoreData 0x00007fff82c28c06 -[NSManagedObject initWithEntity:insertIntoManagedObjectContext:] + 182
3 CoreData 0x00007fff82d4d3dc +[PFUbiquityPeer(UbiquityMethods) peerForPeerID:inManagedObjectContext:createIfMissing:] + 364
4 CoreData 0x00007fff82d4f809 -[PFUbiquityPeerRange(UbiquityMethods) loadFromStoreMetadataDictionary:] + 105
5 CoreData 0x00007fff82d80372 -[PFUbiquityStoreMetadataMedic recoverPeerRangesWithError:] + 418
6 CoreData 0x00007fff82d80ab5 -[PFUbiquityStoreMetadataMedic recoverMetadataWithError:] + 1749
7 CoreData 0x00007fff82d831dc -[PFUbiquitySetupAssistant performPostStoreSetupWithStore:error:] + 732
8 CoreData 0x00007fff82c04001 -[NSPersistentStoreCoordinator addPersistentStoreWithType:configuration:URL:options:error:] + 3537
9 MyApp 0x000000010323de60 -[AppDelegate persistentStoreCoordinator] + 4224
10 MyApp 0x000000010323e43f -[AppDelegate managedObjectContext] + 95
11 Foundation 0x00007fff863b5384 _NSGetUsingKeyValueGetter + 62
12 Foundation 0x00007fff863b5339 -[NSObject(NSKeyValueCoding) valueForKey:] + 392
13 Foundation 0x00007fff863d4dc6 -[NSObject(NSKeyValueCoding) valueForKeyPath:] + 348
14 AppKit 0x00007fff87fb1ae2 -[NSBinder _valueForKeyPath:ofObject:mode:raisesForNotApplicableKeys:] + 654
15 AppKit 0x00007fff87fb17cc -[NSBinder valueForBinding:resolveMarkersToPlaceholders:] + 171
16 AppKit 0x00007fff87fb143a -[NSObjectParameterBinder _updateObject:observedController:observedKeyPath:context:] + 1181
17 AppKit 0x00007fff87fa3777 -[NSObject(NSKeyValueBindingCreation) bind:toObject:withKeyPath:options:] + 591
18 AppKit 0x00007fff87f9ca89 -[NSIBObjectData nibInstantiateWithOwner:topLevelObjects:] + 1079
19 AppKit 0x00007fff87f9309f loadNib + 322
20 AppKit 0x00007fff87f9259c +[NSBundle(NSNibLoading) _loadNibFile:nameTable:withZone:ownerBundle:] + 217
21 AppKit 0x00007fff87f924b7 +[NSBundle(NSNibLoading) loadNibFile:externalNameTable:withZone:] + 141
22 AppKit 0x00007fff87f923fa +[NSBundle(NSNibLoading) loadNibNamed:owner:] + 364
23 AppKit 0x00007fff882059b3 NSApplicationMain + 398
24 MyApp 0x0000000103239522 main + 34
25 MyApp 0x00000001032394f4 start + 52
26 ??? 0x0000000000000003 0x0 + 3
)
terminate called throwing an exception(lldb)
如果我没有将NSPersistentStoreUbiquitousContentNameKey和NSPersistentStoreUbiquitousContentURLKey选项添加到商店，一切都可以正常运行。我只在每两次应用程序启动时获得此异常。出于测试目的（并且因为我认为该问题可能与并发有关），我从主NIB文件中删除了所有Core Data访问和绑定，并尝试在applicationDidFinishLaunching:方法内以编程方式访问Core Data堆栈。在第一次测试中，我直接执行了此操作，第二次在延迟10秒后执行选择器（managedObjectContext）。两次测试都会在每次第二次应用程序启动时产生相同的异常。
（此示例略有缩短）managedObjectContext方法如下所示：
- (NSManagedObjectContext *)managedObjectContext
{
if (managedObjectContext_)
{
return managedObjectContext_;
}
NSPersistentStoreCoordinator *coordinator = self.persistentStoreCoordinator;
if (!coordinator)
{
return nil;
}
NSManagedObjectContext *moc = [[NSManagedObjectContext alloc]
initWithConcurrencyType:NSMainQueueConcurrencyType];
[moc performBlockAndWait:
^{
moc.mergePolicy = [[NSMergePolicy alloc]
initWithMergeType:NSMergeByPropertyObjectTrumpMergePolicyType];
[moc setPersistentStoreCoordinator:coordinator];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(mergeChangesFrom_iCloud:)
name:NSPersistentStoreDidImportUbiquitousContentChangesNotification
object:coordinator];
}];
managedObjectContext_ = moc;
return managedObjectContext_;
}
persistentStoreCoordinator的相关部分是：
NSMutableDictionary *storeOptions = [NSMutableDictionary dictionary];
[storeOptions setObject:[NSNumber numberWithBool:YES]
forKey:NSMigratePersistentStoresAutomaticallyOption];
[storeOptions setObject:[NSNumber numberWithBool:YES]
forKey:NSInferMappingModelAutomaticallyOption];
NSURL *url = [NSURL fileURLWithPath:[applicationSupportDirectory
stringByAppendingPathComponent:kJCMyAppDatabaseFilename]];
NSURL *ubiquityURL = [[NSFileManager defaultManager]
URLForUbiquityContainerIdentifier:nil];
if (ubiquityURL)
{
JCDLog(@"User has iCloud enabled.");
[storeOptions setObject:@"com.juicycocktail.myapp"
forKey:NSPersistentStoreUbiquitousContentNameKey];
[storeOptions setObject:[NSURL fileURLWithPath:[[ubiquityURL path]
stringByAppendingPathComponent:kJCMyAppDatabaseFilename]]
forKey:NSPersistentStoreUbiquitousContentURLKey];
}
persistentStoreCoordinator_ = [[NSPersistentStoreCoordinator alloc]
initWithManagedObjectModel:mom];
NSPersistentStoreCoordinator *psc = persistentStoreCoordinator_;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),
(dispatch_block_t)^{
[psc lock];
if (![psc addPersistentStoreWithType:kJCMyAppStoreType
configuration:nil URL:url options:storeOptions error:&error])
{
dispatch_async(dispatch_get_main_queue(),
^{
[[NSApplication sharedApplication] presentError:error];
persistentStoreCoordinator_ = nil;
return;
});
}
[psc unlock];
dispatch_async(dispatch_get_main_queue(),
^{
JCDLog(@"asynchronously added persistent store!");
[[NSNotificationCenter defaultCenter]
postNotificationName:@"RefetchAllDatabaseData"
object:self userInfo:nil];
});
});
return persistentStoreCoordinator_;
我猜PFUbiquityPeer类可能与保存在iCloud的移动文档文件夹中的Core Data的事务日志有关，但我仍然无法找到导致此问题的真正原因。任何有关如何跟踪此异常的根的帮助都非常受欢迎，因为我已经疯了。特别是解决方法甚至解决方案对我来说非常有帮助。如果有人提示如何至少追查这个异常，我也很高兴。
注意：如果这是一个API错误（rdar：// 10892613），我也提交了一个错误。