核心数据一对多关系 CoreData Generated Accessors

Question

我有一个一对多的 coredata 项目。这是我的 .h：

@class Categories, Tags;

@interface Content : NSManagedObject

@property (nonatomic, retain) NSString * title;
@property (nonatomic, retain) NSString * body;
@property (nonatomic, retain) Categories *category;
@property (nonatomic, retain) NSSet *tags;
@end

@interface Content (CoreDataGeneratedAccessors)

- (void)addTagsObject:(Tags *)value;
- (void)removeTagsObject:(Tags *)value;
- (void)addTags:(NSSet *)values;
- (void)removeTags:(NSSet *)values;

这是我的实现：

    NSError *error = nil;

    // Categories:

    NSManagedObjectContext *moc = [self managedObjectContext];
    NSEntityDescription *contentDescription = [ NSEntityDescription entityForName:@"Categories" inManagedObjectContext:moc];

    NSFetchRequest *categoRequest = [NSFetchRequest new];
    categoRequest.entity = contentDescription;
    NSPredicate *categoPredicate = [NSPredicate predicateWithFormat:@"category like %@", _dropMenuOulet.stringValue];
    categoRequest.predicate = categoPredicate;

    NSArray *results = [moc executeFetchRequest:categoRequest error:&error];

    Categories *catego = (Categories*) [results objectAtIndex:0];

//    Tags:

    NSEntityDescription *tagsDescription = [ NSEntityDescription entityForName:@"Tags" inManagedObjectContext:moc];
    NSFetchRequest *tagsRequest = [NSFetchRequest new];
    tagsRequest.entity = tagsDescription;
    NSArray *tagsResults = [moc executeFetchRequest:tagsRequest error:&error];

    NSMutableArray *tagArray = [ NSMutableArray new];


    for (NSManagedObject *obj in tagsResults)
    {

        //firstName = [obj valueForKey:@"firstName"];
        Tags *storeTag = [obj valueForKey:@"tag"];
        [tagArray addObject:storeTag];
    }
    Content *content1 = [NSEntityDescription insertNewObjectForEntityForName:@"Content" inManagedObjectContext:moc];

    content1.category = catego;
    content1.title = _titleOutlet.stringValue;
    content1.body = _bodyOutlet.stringValue;

    NSMutableSet  *tagSet = [NSMutableSet set];

    for (int i = 0 ; i <tagArray.count; i++)
    {
        Tags *myTag = [tagArray objectAtIndex:i ];
        [tagSet addObject:myTag];

    }

    content1.tags = tagSet;

但是在这一行“content1.tags = tagSet;”我收到以下错误：

[NSTaggedPointerString managedObjectContext]: unrecognized selector sent to instance 0x696669637355
NSTaggedPointerString managedObjectContext]: unrecognized selector sent to instance 0x696669637355

如果您知道我做错了什么导致该错误，我将不胜感激。

Answer 1

看起来您的 NSMutableSet *tagSet 包含不是 Tags 实例的对象（可能是 NSString 实例）。

在这些方面：

Tags *storeTag = [obj valueForKey:@"tag"];
[tagArray addObject:storeTag];

您添加的是tag 属性，而不是Tags 实例本身。

也许只需将这两行替换为：

[tagArray addObject:obj];