How to use MPMediaQuery with UIWebView. Show album informations via Javascript function.

gistfile1.m

-(void)fetchAlbums
{
    MPMediaQuery *albumQuery = [MPMediaQuery albumsQuery];
    NSMutableArray *albums = [@[] mutableCopy];
    NSDateFormatter* formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"YYYY-MM-dd"];

    NSArray *jsonKeysAndValues =
    @[
      @{ @"key": @"MPMediaEntityPropertyPersistentID",   @"value" : MPMediaEntityPropertyPersistentID },
      @{ @"key": @"MPMediaItemPropertyMediaType",        @"value" : MPMediaItemPropertyMediaType },
      @{ @"key": @"MPMediaItemPropertyTitle",            @"value" : MPMediaItemPropertyTitle },
      @{ @"key": @"MPMediaItemPropertyAlbumTitle",       @"value" : MPMediaItemPropertyAlbumTitle },
      @{ @"key": @"MPMediaItemPropertyArtist",           @"value" : MPMediaItemPropertyArtist },
      @{ @"key": @"MPMediaItemPropertyAlbumArtist",      @"value" : MPMediaItemPropertyAlbumArtist },
      @{ @"key": @"MPMediaItemPropertyGenre",            @"value" : MPMediaItemPropertyGenre },
      @{ @"key": @"MPMediaItemPropertyComposer",         @"value" : MPMediaItemPropertyComposer },
      @{ @"key": @"MPMediaItemPropertyPlaybackDuration", @"value" : MPMediaItemPropertyPlaybackDuration },
      @{ @"key": @"MPMediaItemPropertyAlbumTrackNumber", @"value" : MPMediaItemPropertyAlbumTrackNumber },
      @{ @"key": @"MPMediaItemPropertyAlbumTrackCount",  @"value" : MPMediaItemPropertyAlbumTrackCount },
      @{ @"key": @"MPMediaItemPropertyDiscNumber",       @"value" : MPMediaItemPropertyDiscNumber },
      @{ @"key": @"MPMediaItemPropertyDiscCount",        @"value" : MPMediaItemPropertyDiscCount },
      @{ @"key": @"MPMediaItemPropertyArtwork",          @"value" : MPMediaItemPropertyArtwork },
      @{ @"key": @"MPMediaItemPropertyLyrics",           @"value" : MPMediaItemPropertyLyrics },
      @{ @"key": @"MPMediaItemPropertyIsCompilation",    @"value" : MPMediaItemPropertyIsCompilation },
      @{ @"key": @"MPMediaItemPropertyReleaseDate",      @"value" : MPMediaItemPropertyReleaseDate },
      @{ @"key": @"MPMediaItemPropertyBeatsPerMinute",   @"value" : MPMediaItemPropertyBeatsPerMinute },
      @{ @"key": @"MPMediaItemPropertyComments",         @"value" : MPMediaItemPropertyComments },
      @{ @"key": @"MPMediaItemPropertyAssetURL",         @"value" : MPMediaItemPropertyAssetURL },
      // Podcast Item Property Keys or User-Defined Property Keys
      @{ @"key": @"MPMediaItemPropertyPlayCount",        @"value" : MPMediaItemPropertyPlayCount },
      @{ @"key": @"MPMediaItemPropertySkipCount",        @"value" : MPMediaItemPropertySkipCount },
      @{ @"key": @"MPMediaItemPropertyRating",           @"value" : MPMediaItemPropertyRating },
      @{ @"key": @"MPMediaItemPropertyLastPlayedDate",   @"value" : MPMediaItemPropertyLastPlayedDate },
      @{ @"key": @"MPMediaItemPropertyUserGrouping",     @"value" : MPMediaItemPropertyUserGrouping },
      @{ @"key": @"MPMediaItemPropertyBookmarkTime",     @"value" : MPMediaItemPropertyBookmarkTime }
      ];
    for (MPMediaItemCollection *collection in [albumQuery collections]) {
        NSMutableDictionary *album = [@{} mutableCopy];
        MPMediaItem *song = [collection representativeItem];

        for (NSDictionary *dict in jsonKeysAndValues) {
            if (
                [song respondsToSelector:NSSelectorFromString(dict[@"value"])] &&
                [song valueForKey:dict[@"value"]] != nil
            ) {
                if ([dict[@"key"] isEqualToString:@"MPMediaItemPropertyArtwork"]) {
                    UIImage *artworkImage = [[song valueForKey:dict[@"value"]] imageWithSize:CGSizeMake(90.0, 90.0)];
                    NSData *imageData = UIImageJPEGRepresentation(artworkImage, 1.0);
                    if (imageData) {
                        //album[ dict[@"key"] ] = [self imageDataToBase64String:imageData];
                        album[ dict[@"key"] ] = [self imageDataToFilePath:imageData fileName:[song valueForKey:MPMediaEntityPropertyPersistentID]];
                    }
                } else if (
                    [dict[@"key"] isEqualToString:@"MPMediaItemPropertyReleaseDate"] ||
                    [dict[@"key"] isEqualToString:@"MPMediaItemPropertyLastPlayedDate"]
                ) {
                    album[ dict[@"key"] ] = [formatter stringFromDate:[song valueForKey:dict[@"value"]]];
                } else {
                    album[ dict[@"key"] ] = [song valueForKey:dict[@"value"]];
                }
            }
        }
        [albums addObject:album];
    }
    NSError *error;
    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:albums
                                                       options:0
                                                         error:&error
                        ];
    if (!jsonData) {
        NSLog(@"ERROR %@", [error description]);
    } else {
        NSString *jsonStr = [[NSString alloc] initWithBytes:[jsonData bytes]
                                                     length:[jsonData length]
                                                   encoding:NSUTF8StringEncoding
                             ];
        NSString *js = [NSString stringWithFormat:@"someFunction(%@);", jsonStr];
        [webView_ stringByEvaluatingJavaScriptFromString:js];
    }
}

- (NSString*) imageDataToBase64String:(NSData *)imageData
{
    return [imageData base64EncodedString];
}

- (NSString*) imageDataToFilePath:(NSData *)imageData fileName:(NSString *)fileName
{
    NSString *savePath = [NSString stringWithFormat:@"Documents/%@.jpg", fileName];
    savePath = [NSHomeDirectory() stringByAppendingPathComponent:savePath];
    if (![[NSFileManager defaultManager] fileExistsAtPath:savePath]) {
        [imageData writeToFile:savePath atomically:YES];
    }
    return [NSString stringWithFormat:@"file://%@", savePath];
}