CoreData to-many添加错误

不知道我在这里做错了什么。

学校对学生有很多，学生有反向。

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一点测试代码如下：

@class Student; @interface School : NSManagedObject @property (nonatomic, retain) NSString * name; @property (nonatomic, retain) NSOrderedSet *students; @end @interface School (CoreDataGeneratedAccessors) - (void)insertObject:(Student *)value inStudentsAtIndex:(NSUInteger)idx; - (void)removeObjectFromStudentsAtIndex:(NSUInteger)idx; - (void)insertStudents:(NSArray *)value atIndexes:(NSIndexSet *)indexes; - (void)removeStudentsAtIndexes:(NSIndexSet *)indexes; - (void)replaceObjectInStudentsAtIndex:(NSUInteger)idx withObject:(Student *)value; - (void)replaceStudentsAtIndexes:(NSIndexSet *)indexes withStudents:(NSArray *)values; - (void)addStudentsObject:(Student *)value; - (void)removeStudentsObject:(Student *)value; - (void)addStudents:(NSOrderedSet *)values; - (void)removeStudents:(NSOrderedSet *)values; @end // Meanwhile, elsewhere... -(void)go { AppDelegate *app = (AppDelegate *)[[UIApplication sharedApplication] delegate]; NSManagedObjectContext *context = [app managedObjectContext]; School *school = (School *)[NSEntityDescription insertNewObjectForEntityForName:@"School" inManagedObjectContext:context]; [school setName:@"Stanford"]; Student *student = (Student *)[NSEntityDescription insertNewObjectForEntityForName:@"Student" inManagedObjectContext:context]; [student setName:@"Eric"]; //[school addStudentsObject:student]; NSMutableSet *students = [school mutableSetValueForKey:@"students"]; [students addObject:student]; NSError *__autoreleasing error; BOOL success = [context save:&error]; if (!success) { @throw [NSException exceptionWithName:NSGenericException reason:[error description] userInfo:nil]; } } 

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使用注释的addStudentsObject:失败：

 2013-04-13 16:22:58.648 CDTMTest[2098:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSSet intersectsSet:]: set argument is not an NSSet' *** First throw call stack: (0x1fa2012 0x13dfe7e 0x2030a4a 0xb85ec6 0xb087f9 0xb85d33 0x11aa638 0x7ee2069 0x2b4d 0xacd5b3 0x1f61376 0x1f60e06 0x1f48a82 0x1f47f44 0x1f47e1b 0x1efc7e3 0x1efc668 0x13ffc 0x1bdd 0x1b05) libc++abi.dylib: terminate called throwing an exception 

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使用mutableSetValueForKey:失败

 2013-04-13 16:07:05.111 CDTMTest[2012:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'NSManagedObjects of entity 'School' do not support -mutableSetValueForKey: for the property 'students'' *** First throw call stack: (0x1fa3012 0x13e0e7e 0x11370da 0x3af3 0xace5b3 0x1f62376 0x1f61e06 0x1f49a82 0x1f48f44 0x1f48e1b 0x1efd7e3 0x1efd668 0x14ffc 0x2b7d 0x2aa5) libc++abi.dylib: terminate called throwing an exception 

Answer 1

您可能想尝试将其添加到集合中：

 mutableOrderedSetValueForKey: 

因为你选择了许多关系来订购。 但我相信你会更容易设置另一种关系：

 student.school = school; 

Answer 2

我有类似的问题。 我在某处读到，对于多对多关系的基本核心数据实现始终无法正常工作。 它与仅接受nsset并且生成的setter没有正确地将传入参数转换为nsset的关系有关。 要解决此问题，请尝试使用以下内容覆盖addStudentsObject：方法：

 static NSString *const kItemsKey = @"students"; - (void)addStudentsObject:(Student *)value { NSMutableSet* tempSet = [NSMutableSet setWithSet:self.students]; NSSet* newObject = [NSSet setWithObject:value]; [self willChangeValueForKey:kItemsKey withSetMutation:NSKeyValueUnionSetMutation usingObjects:newObject]; [tempSet addObject:value]; self.students = tempSet; [self didChangeValueForKey:kItemsKey withSetMutation:NSKeyValueUnionSetMutation usingObjects:newObject]; }