如何为NSOrderedSet添加元素以获取Core Data？

Question

我对这篇文章做了一些研究.但它的解决方案都不适合我.让我解释一下我做了什么:

它实际上与上述帖子非常相似.

Category.h

@class Category, Item;

@interface Category : NSManagedObject

@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) NSOrderedSet *items;
@property (nonatomic, retain) Category *parentcategory;
@property (nonatomic, retain) NSSet *subcategories;

@end

@interface Category (CoreDataGeneratedAccessors)

- (void)insertObject:(Item *)value inItemsAtIndex:(NSUInteger)idx;
- (void)removeObjectFromItemsAtIndex:(NSUInteger)idx;
- (void)insertItems:(NSArray *)value atIndexes:(NSIndexSet *)indexes;
- (void)removeItemsAtIndexes:(NSIndexSet *)indexes;
- (void)replaceObjectInItemsAtIndex:(NSUInteger)idx withObject:(Item *)value;
- (void)replaceItemsAtIndexes:(NSIndexSet *)indexes withItems:(NSArray *)values;
- (void)addItemsObject:(Item *)value;
- (void)removeItemsObject:(Item *)value;
- (void)addItems:(NSOrderedSet *)values;
- (void)removeItems:(NSOrderedSet *)values;
- (void)addSubcategoriesObject:(Category *)value;
- (void)removeSubcategoriesObject:(Category *)value;
- (void)addSubcategories:(NSSet *)values;
- (void)removeSubcategories:(NSSet *)values;

@end

在我的视图控制器中,我加载了以下类别之一:

NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:kEntityCategory];
request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor
                                                    sortDescriptorWithKey:kAttributeCategoryName ascending:YES
                                                    selector:@selector(localizedCaseInsensitiveCompare:)]];

NSError *error = nil;
AppDelegate* appDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate;

NSArray* data = [appDelegate.dataCenter.document.managedObjectContext executeFetchRequest:request error:&error];
if ( data.count > 0)
{
    self.category = [data objectAtIndex:0];
}

我在导航栏中有一个按钮用于测试目的.当它被点击时,我将复制第一个项目并添加到最后.

Item* item = [self.category.items objectAtIndex:0];

[self.category willChangeValueForKey:@"items"];
NSMutableOrderedSet *tempSet = [NSMutableOrderedSet orderedSetWithOrderedSet:self.category.items];
[tempSet addObject: item];
self.category.items = tempSet;
[self.category didChangeValueForKey:@"items"];

问题是该项目根本没有添加到数据库中.(我做了一些测试,例如,我修改了项目内容.它证明数据库完全没有问题.)但我不知道该项目不是数据库的原因.有人可以帮忙吗？谢谢

Answer 1

迅速:

let mutableItems = items.mutableCopy() as! NSMutableOrderedSet
mutableItems.addObject(anItem)
items = mutableItems.copy() as! NSOrderedSet

Objective-C的:

NSMutableOrderedSet *mutableItems = (NSMutableOrderedSet *)items.mutableCopy;
[mutableItems addObject:anItem];
items = (NSOrderedSet *)mutableItems.copy;

Answer 2

问题解决了。有两个问题：

1. 无法插入/添加现有项目
2. 我有一个愚蠢的名称冲突。所以这篇文章中的建议是好的。

谢谢。