目前我正在开发一个使用CoreData 和 NSFectchedResults 控制器的应用程序。 此应用程序仅包含一个使用 NSFedResults 控制器的 UIT View 。
启动应用程序时, 另一个线条被分离。 在这个新线条中, 一个 WS 调用许可从网络服务器获取数据。 WS 调用后, 我将数据存储在 CoreData DB 中, 并存到另一个NSManageedObjectCortext (Apple the practice: another dress {gt; 另外一个上下文) 。 在保存新对象之前, 我不得不删除此实体的所有对象 。 我通过合并 CchangesFrom ContextedSave notification 将此其它上下文与主上下文合并 。
// Data Manager (in another thread)
NSManagedObjectContext *context = [[NSManagedObjectContext alloc] init];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(contextDidSave:)
name:NSManagedObjectContextDidSaveNotification
object:context];
[context setMergePolicy:NSMergeByPropertyObjectTrumpMergePolicy];
[context setPersistentStoreCoordinator:[self getPersistentStoreCoordinator]];
...
for (NSManagedObject * obj in objects)
{
[context deleteObject:obj];
}
...
for(NSDictionary *serverObj in serverObjects)
{
objAd = [NSEntityDescription
insertNewObjectForEntityForName:@"MyEntity"
inManagedObjectContext:context];
...
}
[context save:&error];
[[NSNotificationCenter defaultCenter] removeObserver:self name:NSManagedObjectContextDidSaveNotification object:context];
[context release];
...
- (void)contextDidSave:(NSNotification *)notification
{
SEL selector = @selector(mergeChangesFromContextDidSaveNotification:);
[[self getContext] performSelectorOnMainThread:selector withObject:notification waitUntilDone:YES];
}
- (NSManagedObjectContext *) getContext
{
return [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
}
- (NSPersistentStoreCoordinator *) getPersistentStoreCoordinator
{
return [(AppDelegate *)[[UIApplication sharedApplication] delegate] persistentStoreCoordinator];
}
<% 2> 这是我的NSFectchedResults 主计长的抓手:
// UIView
- (NSFetchedResultsController*) offersFRC {
if (offersFRC == nil)
{
NSManagedObjectContext *l_ManagedObjectContext = [[DataManager sharedDataManager] getContext];
NSFetchRequest *l_FetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *l_Entity = [NSEntityDescription entityForName:@"MyEntity" inManagedObjectContext:l_ManagedObjectContext];
[l_FetchRequest setEntity:l_Entity];
[l_FetchRequest setFetchBatchSize:5];
NSNumber *sortType = [self.searchCriterions objectForKey:@"sortType"];
NSSortDescriptor *l_SortDescriptor = [[NSSortDescriptor alloc] initWithKey:[Constants getFieldNameBySortType:sortType] ascending:[Constants isAscendingBySortType:sortType]];
[l_FetchRequest setSortDescriptors:[NSArray arrayWithObjects:l_SortDescriptor, nil]];
[l_SortDescriptor release];
NSFetchedResultsController *l_FetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:l_FetchRequest managedObjectContext:l_ManagedObjectContext
sectionNameKeyPath:nil
cacheName:nil];
[l_FetchRequest release];
[self setOffersFRC:l_FetchedResultsController];
[l_FetchedResultsController release],l_FetchedResultsController = nil;
[self.offersFRC setDelegate:self];
}
return offersFRC;
}
<% 1 > 3/ 应用程序启动时,我遇到以下错误 :
2012-02-29 11:56:09.119 Nanopost[1996:207] *** Terminating app due to uncaught exception NSObjectInaccessibleException , reason: CoreData could not fulfill a fault for 0x5c3c760 <x-coredata://E176B0A1-275B-4332-9231-49FD88238C2B/Ads/p231>
*** Call stack at first throw:
(
0 CoreFoundation 0x02bfe919 __exceptionPreprocess + 185
1 libobjc.A.dylib 0x02e595de objc_exception_throw + 47
2 CoreData 0x028b833f _PFFaultHandlerLookupRow + 1407
3 CoreData 0x028b5ee3 _PF_FulfillDeferredFault + 499
4 CoreData 0x028b9f3f _sharedIMPL_pvfk_core + 95
5 CoreData 0x0292a010 _PF_Handler_Public_GetProperty + 160
6 Foundation 0x02442c4f -[NSSortDescriptor compareObject:toObject:] + 128
7 CoreData 0x0297db5e +[NSFetchedResultsController(PrivateMethods) _insertIndexForObject:inArray:lowIdx:highIdx:sortDescriptors:] + 286
8 CoreData 0x0297e1b2 -[NSFetchedResultsController(PrivateMethods) _postprocessInsertedObjects:] + 402
9 CoreData 0x029841bc -[NSFetchedResultsController(PrivateMethods) _managedObjectContextDidChange:] + 1804
10 Foundation 0x02380c1d _nsnote_callback + 145
11 CoreFoundation 0x02bd6cf9 __CFXNotificationPost_old + 745
12 CoreFoundation 0x02b5611a _CFXNotificationPostNotification + 186
13 Foundation 0x023767c2 -[NSNotificationCenter postNotificationName:object:userInfo:] + 134
14 CoreData 0x028c0519 -[NSManagedObjectContext(_NSInternalNotificationHandling) _postObjectsDidChangeNotificationWithUserInfo:] + 89
15 CoreData 0x028f802b -[NSManagedObjectContext mergeChangesFromContextDidSaveNotification:] + 1579
16 Foundation 0x02395e9a __NSThreadPerformPerform + 251
17 CoreFoundation 0x02bdfd7f __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
18 CoreFoundation 0x02b3e2cb __CFRunLoopDoSources0 + 571
19 CoreFoundation 0x02b3d7c6 __CFRunLoopRun + 470
20 CoreFoundation 0x02b3d280 CFRunLoopRunSpecific + 208
21 CoreFoundation 0x02b3d1a1 CFRunLoopRunInMode + 97
22 GraphicsServices 0x031e62c8 GSEventRunModal + 217
23 GraphicsServices 0x031e638d GSEventRun + 115
24 UIKit 0x0063cb58 UIApplicationMain + 1160
25 Nanopost 0x0000230a main + 170
26 Nanopost 0x00002255 start + 53
)
terminate called after throwing an instance of _NSCoreDataException
<强度 > 进口说明 :
- It crashes only on iOS4
- controllerWillChangeContent is the last function called in my code before application s crash. controllerDidChangeContent / didChangeObject/ didChangeSection are not called.
- When I comment [l_FetchRequest setFetchBatchSize:5] => No more crashes
- When I add a [context save:&error] after objects deletion and before new objects insertion => No more crashes
- When I use [l_FetchRequest setFetchBatchSize:24] => Crashes
- When I use [l_FetchRequest setFetchBatchSize:25] => No more crashes
我花了很多时间试图理解这个问题,
托马斯·托马斯
Edit 1 (@Jody): Hi Jody and thank you very much for your answers!
以下是用于处理上下文的代码 是否保存 :
- (void)contextDidSave:(NSNotification *)notification
{
SEL selector = @selector(mergeChangesFromContextDidSaveNotification:);
[[self getContext] performSelectorOnMainThread:selector withObject:notification waitUntilDone:YES];
}
"你必须先告诉我更多关于你使用的上下文":
我在此应用程序中使用了 2 个上下文 :
N° 1 : 在创建 XCode Project 时默认创建于 AppDelegate 中。 此上下文被我的 FRC 使用, 并允许显示 UITView 的行 。
第2点:在我的“数据管理器”(我的文章中的第一个代码块)中创建,一个允许刷新我的DB(WS呼叫、删除、重新插入、保存)的单吨。
当保存了第2号上下文时, 上下文Save 被调用将上下文与主上下文( 文本编号 1: ) 合并为上下文 。 在此之后, 我的 FRC 代表方法“ 控制器 Will Change Content ” 被调用 。 我不认为它有助于显示此方法所含的代码, 因为即使我刚刚放了一个NSLog, 它也随此方法而崩溃( 我将许多 NSLog 和 NSLog 包含在控制器 WillChange Content 中的 NSLog 是崩溃前显示的最后一个 ) 。