Question

I have a webservice with the following structure.

{

    "media": {
        "albums": [
            {
                "name": "FC Bazel - KRC Genk",
                "date": "04.10.2012",
                "pictures": [
                    {
                        "url": "http://www.krcgenk.be/images/gallery/album_198/800X600/8162f172f8e5739c535c97b7bb6ca276.jpg"
                    },
                    {
                        "url": "http://www.krcgenk.be/images/gallery/album_198/800X600/5635d20351aacef78563dee347468227.jpg"
                    }
]

I am saving my Albums and Pictures in a separate entity in my core data database. I am getting the values the following.

+ (NSArray *)getAlbums
{
    NSString *request = [NSString stringWithFormat:@"http://www.krcgenk.be/mobile/json/request/media/type/ipad"];
    return [[self executeGenkFetch:request] valueForKeyPath:@"media.albums"];
}
+ (NSArray *)getPictures
{
    NSString *request = [NSString stringWithFormat:@"http://www.krcgenk.be/mobile/json/request/media/type/ipad"];
    return [[self executeGenkFetch:request] valueForKeyPath:@"media.albums.pictures"];
}

And I define the values like following.

#define ALBUMS_NAME @"name"
#define ALBUMS_DATE @"date"

#define PICTURES_URL @"pictures.url"

All things work great for albums. But when it tries to get the url in pictures, it crashes with the following error.

__NSArrayI objectForKey:]: unrecognized selector sent to instance 0xa48a460
2012-10-05 17:06:50.201 RacingGenk[97248:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayI objectForKey:]: unrecognized selector sent to instance 0xa48a460

Can someone help?

Kind regards.

—–EDIT—-

+ (Picture *)pictureWithGenkInfo:(NSDictionary *)genkInfo
          inManagedObjectContext:(NSManagedObjectContext *)context
                     withAlbumId:(int)albumId
                   withPictureId:(int)pictureId;
{

    Picture *picture = nil;

    picture = [NSEntityDescription insertNewObjectForEntityForName:@"Picture"
                                          inManagedObjectContext:context];
    NSLog(@"methode komt tot hier");
    picture.url                     = [genkInfo objectForKey:PICTURES_URL];

return picture
}

‘

Answer 1

You can get the albums with media.albums because albums is the value for the key “media”, but “pictures” is not the value of the key albums — the value is an array (hence your error message) of dictionaries. I don’t know if this will work, but you could try this:

NSArray *arr = [[self executeGenkFetch:request] valueForKeyPath:@"media.albums"];
return [[arr objectAtIndex:0] valueForKey:@"pictures"];