Play iPod playlist retrieved from a saved persistentid list

MPMediaItemCollectionSavePlaylist.m

- (void) mediaPicker: (MPMediaPickerController *) mediaPicker didPickMediaItems: (MPMediaItemCollection *) mediaItemCollection {
    [self savePlaylist:mediaItemCollection];
    [self dismissModalViewControllerAnimated: YES];
}


- (void)savePlaylist:(MPMediaItemCollection *) mediaItemCollection {
    NSArray* items = [mediaItemCollection items];
    NSMutableArray* listToSave = [[NSMutableArray alloc] initWithCapacity:0];=
    for (MPMediaItem *song in items) {
        NSNumber *persistentId = [song valueForProperty:MPMediaItemPropertyPersistentID];
        [listToSave addObject:persistentId];
    }
    NSData *data = [NSKeyedArchiver archivedDataWithRootObject: listToSave];
    [[NSUserDefaults standardUserDefaults] setObject:data forKey:@"songsList"];
    [[NSUserDefaults standardUserDefaults] synchronize];
    [listToSave release];
}


- (void)setupMusic {
    myPlayer = [MPMusicPlayerController applicationMusicPlayer];
    if ([[NSUserDefaults standardUserDefaults] objectForKey:@"songsList"] != nil) {
        NSMutableArray *theList = [[NSMutableArray alloc] initWithCapacity:0];
        NSData *data = [[NSUserDefaults standardUserDefaults] objectForKey:@"songsList"];
        NSArray *decodedData = [NSKeyedUnarchiver unarchiveObjectWithData:data];
        [theList addObjectsFromArray:decodedData];
        NSMutableArray *allTheSongs = [[NSMutableArray alloc] initWithCapacity:0];
        for (int i = 0; i < [theList count]; i++) {
            MPMediaQuery *songQuery = [MPMediaQuery songsQuery];
            [songQuery addFilterPredicate:[MPMediaPropertyPredicate predicateWithValue:[theList objectAtIndex:i] forProperty:MPMediaItemPropertyPersistentID]];
            NSArray *songs = [songQuery items];
            [allTheSongs addObjectsFromArray: songs];
        }
        MPMediaItemCollection *currentQueue = [[MPMediaItemCollection alloc] initWithItems:allTheSongs];
        [myPlayer setQueueWithItemCollection:currentQueue];
        [theList release];
        [currentQueue release];
        [allTheSongs release];
    } else {
        [myPlayer setQueueWithQuery: [MPMediaQuery songsQuery]];
        [myPlayer setShuffleMode: MPMusicShuffleModeSongs]; //optional
    }
}