核心数据NSManagedObject isFault在prepareForDeletion中
我在- prepareForDeletion的{{1}}内进行了一些处理。但是，当我尝试访问此类的某些属性时，它们将以NSManagedObject的形式返回给我（即使我知道它们不是nil）。所以我检查我的对象是否有错nil并返回[self isFault]。
那么当我在YES内时，如何让对象“无故障”，因为我需要访问一个属性？
PhoneGroup.m（NSManagedObject）
- prepareForDeletion型号信息：
- (void)prepareForDeletion {
[super prepareForDeletion];
NSArray *individuals = [self.individuals allObjects]; // individuals is nil
for (int i = 0; i < [individuals count]; i++) {
Individual *individual = [individuals objectAtIndex:i];
BOOL individualExistsInOtherGroups = [individual.phoneGroups count] > 1;
BOOL individualAddedAsAdditionalContactToReminder = [individual.reminders count] > 0;
// We can delete the individual if individual does not exist in other groups and is not added to any reminders
if (!individualExistsInOtherGroups && !individualAddedAsAdditionalContactToReminder && ![individual isDeleted]) {
[[CoreDataHelper sharedInstance] deleteEntity:individual inManagedObjectContext:self.managedObjectContext];
}
}
// Post a notification to notify all interested VC so they can refresh the GUI
[[NSNotificationCenter defaultCenter] postNotificationName:RMContactDeletedNotification object:self];
DLog(@"Contact deleted notification sent");
}
与PhoneGroup的反比关系与删除规则无效。
Individual与Individual的反比关系与删除规则无效。
PhoneGroup是Contact和Individual s的超类
这是一个可以更好地可视化的图像。
编辑：我在这个问题上做了一些更多的发现
当与PhoneGroup存在关系时， PhoneGroup似乎只会出错。如果Reminder在被删除时与PhoneGroup没有关系，则不错误。
Reminder与Reminder具有可选的反对多关系，并且删除规则为null。
Contact与Contact具有可选的反对多关系，并且删除规则为null。
这给了什么？
编辑2：关于此问题的更多信息
我试图丹雪莉的替代解决方案做了取的ReminderŠ的然而均匀的Individual的{{1}}（self.managedObjectContext）是NSManagedObject在PhoneGroup里面，这意味着什么？
3 个答案:
答案 0 :(得分：1)
[self.individuals allObjects]为什么返回nil？
修改
在发现您的managedObjectContext为nil之后，可以肯定地说您的对象已被其上下文所否定。
这可能是由上下文reset或取消分配引起的，同时您保持对对象的强引用
但是，这并不能解释prepareForDeletion方法中如何发生这种情况
当实时上下文删除对象（[context deleteObject:...]）时，将调用此方法
这意味着要么手动调用prepareForDeletion（[object prepareForDeletion]），要么另一个线程在删除中删除你的上下文。
注意：鉴于您的对象上设置了有效
objectID和实时managedObjectContext，以下代码将有效。
然而，我可能有一个解决方法，因为您访问数据的方式效率低下（稍后会解释）：
如果您删除的对象（PhoneGroup）individuals关系没有出现故障，CoreData将最终访问商店以确定关系（第一次旅行）。然后，您将有错误作为该关系中包含的对象（N个对象），您的循环将逐个访问它们（N次前往商店）。仍然在循环中，您访问每个对象的关系（2个关系发货，phoneGroups和reminders ==＆gt; 2次到商店PER ITEM）。
总结：1 + N + 2 * N = 3 * N + 1次到商店（最坏情况）。
这可以通过更简单的方式实现：
*创建此获取请求：
NSFetchRequest* r = [[NSFetchRequest alloc] initWithEntityName:@"Individual"];
[r setPredicate:[NSPredicate predicateWithFormat:@"%@ IN phoneGroups AND phoneGroups.@count == 1 AND reminders.@count == 0",[self objectID]]];
[r setIncludesPropertyValues:YES];
[r setReturnsObjectsAsFaults:NO];
[r setIncludesPendingChanges:YES];
*现在剩下的就是：
NSManagedObjectContext* context = [self managedObjectContext];
NSArray* individuals = [context executeFetchRequest:r error:NULL];
for (Individual* individual in individuals) {
[context deleteObject:individual];
}
这是通过在最坏的情况下单次（1）到商店旅行来完成的，并且由于您不直接依赖于您的关系，只要您的对象具有objectID，这就应该有效。 BR />
<强> Apendix：
当前的实现性能（SQLite调试）：
//2013-05-19 21:34:42.700 P[9666:c07] CoreData: sql: SELECT 0, t0.Z_PK FROM Z_2PHONEGROUPS t1 JOIN ZCONTACT t0 ON t0.Z_PK = t1.Z_2INDIVIDUALS WHERE t1.Z_3PHONEGROUPS = ?
//2013-05-19 21:34:42.701 P[9666:c07] CoreData: annotation: sql connection fetch time: 0.0004s
//2013-05-19 21:34:42.701 P[9666:c07] CoreData: annotation: total fetch execution time: 0.0008s for 3 rows.
//2013-05-19 21:34:42.715 P[9666:c07] CoreData: annotation: to-many relationship fault "individuals" for objectID 0x8572b70 <x-coredata://CBE585F2-552D-4FDE-AAEA-2C9C7984FAC9/PhoneGroup/p21> fulfilled from database. Got 3 rows
//2013-05-19 21:34:42.716 P[9666:c07] CoreData: sql: SELECT t0.Z_ENT, t0.Z_PK, t0.Z_OPT, t0.ZNAME, t0.ZCONTACTID, t0.ZVISIBLE FROM ZCONTACT t0 WHERE t0.Z_PK = ?
//2013-05-19 21:34:42.717 P[9666:c07] CoreData: annotation: sql connection fetch time: 0.0005s
//2013-05-19 21:34:42.717 P[9666:c07] CoreData: annotation: total fetch execution time: 0.0008s for 1 rows.
//2013-05-19 21:34:42.718 P[9666:c07] CoreData: annotation: fault fulfilled from database for : 0x818cad0 <x-coredata://CBE585F2-552D-4FDE-AAEA-2C9C7984FAC9/Individual/p4>
//2013-05-19 21:34:42.718 P[9666:c07] CoreData: sql: SELECT 0, t0.Z_PK FROM Z_2PHONEGROUPS t1 JOIN ZCONTACT t0 ON t0.Z_PK = t1.Z_3PHONEGROUPS WHERE t1.Z_2INDIVIDUALS = ?
//2013-05-19 21:34:42.719 P[9666:c07] CoreData: annotation: sql connection fetch time: 0.0004s
//2013-05-19 21:34:42.719 P[9666:c07] CoreData: annotation: total fetch execution time: 0.0008s for 1 rows.
//2013-05-19 21:34:42.719 P[9666:c07] CoreData: annotation: to-many relationship fault "phoneGroups" for objectID 0x818cad0 <x-coredata://CBE585F2-552D-4FDE-AAEA-2C9C7984FAC9/Individual/p4> fulfilled from database. Got 1 rows
//2013-05-19 21:34:42.720 P[9666:c07] CoreData: sql: SELECT 0, t0.Z_PK FROM ZREMINDER t0 WHERE t0.ZCONTACT = ?
//2013-05-19 21:34:42.721 P[9666:c07] CoreData: annotation: sql connection fetch time: 0.0005s
//2013-05-19 21:34:42.721 P[9666:c07] CoreData: annotation: total fetch execution time: 0.0008s for 0 rows.
//2013-05-19 21:34:42.721 P[9666:c07] CoreData: annotation: to-many relationship fault "reminders" for objectID 0x818cad0 <x-coredata://CBE585F2-552D-4FDE-AAEA-2C9C7984FAC9/Individual/p4> fulfilled from database. Got 0 rows
//2013-05-19 21:34:42.722 P[9666:c07] CoreData: sql: SELECT t0.Z_ENT, t0.Z_PK, t0.Z_OPT, t0.ZNAME, t0.ZCONTACTID, t0.ZVISIBLE FROM ZCONTACT t0 WHERE t0.Z_PK = ?
//2013-05-19 21:34:42.722 P[9666:c07] CoreData: annotation: sql connection fetch time: 0.0004s
//2013-05-19 21:34:42.722 P[9666:c07] CoreData: annotation: total fetch execution time: 0.0008s for 1 rows.
//2013-05-19 21:34:42.723 P[9666:c07] CoreData: annotation: fault fulfilled from database for : 0x818cb90 <x-coredata://CBE585F2-552D-4FDE-AAEA-2C9C7984FAC9/Individual/p16>
//2013-05-19 21:34:42.723 P[9666:c07] CoreData: sql: SELECT 0, t0.Z_PK FROM Z_2PHONEGROUPS t1 JOIN ZCONTACT t0 ON t0.Z_PK = t1.Z_3PHONEGROUPS WHERE t1.Z_2INDIVIDUALS = ?
//2013-05-19 21:34:42.724 P[9666:c07] CoreData: annotation: sql connection fetch time: 0.0004s
//2013-05-19 21:34:42.724 P[9666:c07] CoreData: annotation: total fetch execution time: 0.0008s for 1 rows.
//2013-05-19 21:34:42.724 P[9666:c07] CoreData: annotation: to-many relationship fault "phoneGroups" for objectID 0x818cb90 <x-coredata://CBE585F2-552D-4FDE-AAEA-2C9C7984FAC9/Individual/p16> fulfilled from database. Got 1 rows
//2013-05-19 21:34:42.725 P[9666:c07] CoreData: sql: SELECT 0, t0.Z_PK FROM ZREMINDER t0 WHERE t0.ZCONTACT = ?
//2013-05-19 21:34:42.725 P[9666:c07] CoreData: annotation: sql connection fetch time: 0.0004s
//2013-05-19 21:34:42.726 P[9666:c07] CoreData: annotation: total fetch execution time: 0.0008s for 0 rows.
//2013-05-19 21:34:42.726 P[9666:c07] CoreData: annotation: to-many relationship fault "reminders" for objectID 0x818cb90 <x-coredata://CBE585F2-552D-4FDE-AAEA-2C9C7984FAC9/Individual/p16> fulfilled from database. Got 0 rows
//2013-05-19 21:34:42.727 P[9666:c07] CoreData: sql: SELECT t0.Z_ENT, t0.Z_PK, t0.Z_OPT, t0.ZNAME, t0.ZCONTACTID, t0.ZVISIBLE FROM ZCONTACT t0 WHERE t0.Z_PK = ?
//2013-05-19 21:34:42.727 P[9666:c07] CoreData: annotation: sql connection fetch time: 0.0004s
//2013-05-19 21:34:42.727 P[9666:c07] CoreData: annotation: total fetch execution time: 0.0008s for 1 rows.
//2013-05-19 21:34:42.728 P[9666:c07] CoreData: annotation: fault fulfilled from database for : 0x818cba0 <x-coredata://CBE585F2-552D-4FDE-AAEA-2C9C7984FAC9/Individual/p17>
//2013-05-19 21:34:42.728 P[9666:c07] CoreData: sql: SELECT 0, t0.Z_PK FROM Z_2PHONEGROUPS t1 JOIN ZCONTACT t0 ON t0.Z_PK = t1.Z_3PHONEGROUPS WHERE t1.Z_2INDIVIDUALS = ?
//2013-05-19 21:34:42.729 P[9666:c07] CoreData: annotation: sql connection fetch time: 0.0004s
//2013-05-19 21:34:42.729 P[9666:c07] CoreData: annotation: total fetch execution time: 0.0008s for 4 rows.
//2013-05-19 21:34:42.729 P[9666:c07] CoreData: annotation: to-many relationship fault "phoneGroups" for objectID 0x818cba0 <x-coredata://CBE585F2-552D-4FDE-AAEA-2C9C7984FAC9/Individual/p17> fulfilled from database. Got 4 rows
//2013-05-19 21:34:42.730 P[9666:c07] CoreData: sql: SELECT 0, t0.Z_PK FROM ZREMINDER t0 WHERE t0.ZCONTACT = ?
//2013-05-19 21:34:42.730 P[9666:c07] CoreData: annotation: sql connection fetch time: 0.0004s
//2013-05-19 21:34:42.731 P[9666:c07] CoreData: annotation: total fetch execution time: 0.0007s for 0 rows.
//2013-05-19 21:34:42.731 P[9666:c07] CoreData: annotation: to-many relationship fault "reminders" for objectID 0x818cba0 <x-coredata://CBE585F2-552D-4FDE-AAEA-2C9C7984FAC9/Individual/p17> fulfilled from database. Got 0 rows
拟议的实施表现：
//2013-05-19 21:13:26.734 P[9609:c07] CoreData: sql: SELECT t0.Z_ENT, t0.Z_PK, t0.Z_OPT, t0.ZNAME, t0.ZCONTACTID, t0.ZVISIBLE FROM ZCONTACT t0 JOIN Z_2PHONEGROUPS t1 ON t0.Z_PK = t1.Z_2INDIVIDUALS WHERE ((t1.Z_3PHONEGROUPS = ? AND (SELECT COUNT(t3.Z_3PHONEGROUPS) FROM Z_2PHONEGROUPS t3 WHERE (t0.Z_PK = t3.Z_2INDIVIDUALS) ) = ? AND (SELECT COUNT(t4.Z_PK) FROM ZREMINDER t4 WHERE (t0.Z_PK = t4.ZCONTACT) ) = ?) AND t0.Z_ENT = ?)
//2013-05-19 21:13:26.735 P[9609:c07] CoreData: annotation: sql connection fetch time: 0.0008s
//2013-05-19 21:13:26.736 P[9609:c07] CoreData: annotation: total fetch execution time: 0.0012s for 2 rows.
数据构建（- (void) synthesizePhoneGroupsAndIndividuals:(NSManagedObjectContext*)context）：
NSMutableArray* individuals = [NSMutableArray new];//[NSEntityDescription insertNewObjectForEntityForName:@"Individual" inManagedObjectContext:context];
for (NSUInteger i = 0; i < (3 + arc4random() % 100); ++i) {
Individual* indi = [NSEntityDescription insertNewObjectForEntityForName:@"Individual" inManagedObjectContext:context];
indi.contactID = [NSString stringWithFormat:@"cid-%u",i];
[individuals addObject:indi];
}
NSMutableArray* groups = [NSMutableArray new];
for (NSUInteger i = 0; i < 3 + arc4random() % 7; ++i) {
PhoneGroup* group = [NSEntityDescription insertNewObjectForEntityForName:@"PhoneGroup" inManagedObjectContext:context];
group.visible = NO;
NSMutableSet* indis = [group mutableSetValueForKey:@"individuals"];
for (NSUInteger j = 0; j < 3; ++j) {
[indis addObject:[individuals objectAtIndex:(arc4random() % [individuals count])]];
}
[groups addObject:group];
}
[context save:NULL];
测试代码：
NSManagedObjectContext* context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
context.persistentStoreCoordinator = _persistentStoreCoordinator;
[context performBlockAndWait:^{
[self synthesizePhoneGroupsAndIndividuals:context];
[context reset];
}];
[context performBlockAndWait:^{
NSFetchRequest* r = [[NSFetchRequest alloc] initWithEntityName:@"PhoneGroup"];
NSArray* groups = [context executeFetchRequest:r error:NULL];
if ([groups count]) {
PhoneGroup* group = [groups objectAtIndex:(arc4random() % [groups count])];
[context deleteObject:group];
}
}];
答案 1 :(得分：0)
我怀疑你的问题可能是因为提前调用[super prepareForDeletion];造成的。你应该做你想做的工作然后打电话[super prepareForDeletion];。
答案 2 :(得分：0)
游戏后期，但我只是遇到了一些类似的问题。
您的商店是否在iCloud上？
我的问题与我在iCloud上使用coredata的事实有关。
即使在调用mergeChangesFromContextDidSaveNotification之前，来自iCloud的已删除对象可能已经无法再访问其属性和相关实体。
我最终没有直接使用任何已删除的对象，也没有依赖prepareForDeletion来访问我需要的数据。
相反，我缓存此信息（在用户设置中适用于我的用例），使用objectID键入。删除后，我使用通知用户信息的NSDeletedObjectsKey中找到的objectID检索该信息。之后删除缓存的信息。
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