What is the proper way of retrieving all SPTracks of an playlist in Cocoalibspotify?

Question

I'm writing an iPhone app that uses cocoalibspotify. In one of my views I want to be able to display all the SPTracks of a playlist in a table view. Each cell should display the Artist, the Album and the Name of the track. I have implemented a method which retrieves the playlist content asynchronously but I haven't figured out the proper way to perform the "converting" of SPPlaylistItems into SPTrack objects on the background thread. As a result, my UI lags everytime I retrieve playlist tracks. Granted, the lag is very minor but it's still annoying. Here is my method that retrieves playlist content.

-(void)getPlaylistContentAsynchronouslyOfPlaylist:(NSString *)playlistName callback:(void (^)(NSArray *playlistTracks))block{
    NSLog(@"Getting content ansynchronously...");
    NSMutableArray *mutableArray = [[NSMutableArray alloc] init];
    SPPlaylist *playlist = [self getPlaylistWithName:playlistName];
    __block BOOL addedAllTracks = mutableArray.count == playlist.items.count;
    for (SPPlaylistItem *item in playlist.items){
        NSLog(@"----Checking Track with url %@", item.itemURL.absoluteString);
        NSURL *trackURL = [item.item spotifyURL];
        [[SPSession sharedSession]trackForURL:trackURL callback:^(SPTrack * spotifyTrack){
            if(spotifyTrack){
                //NSLog(@"---->>>Adding Track with url %@", item.itemURL.absoluteString);
                [mutableArray addObject:spotifyTrack];
            }

            if (mutableArray.count == playlist.items.count){
                //NSLog(@"!!!!!!!Added all songs!");
                addedAllTracks = YES;
            }
        }];
    }

    dispatch_async(self.backgroundQueue, ^{
        NSLog(@"Retrieving playlist content asynchronously...");
        while (!addedAllTracks){
            NSLog(@"<><><><>BG Queue is waiting....");
            [NSThread sleepForTimeInterval:0.25];
        }

        if (block){
            NSLog(@"Done retrieving playlist content asynchronously");
            NSLog(@"*******Passing %d tracks to the caller", mutableArray.count);
            dispatch_async(dispatch_get_main_queue(), ^() { block(mutableArray); });
        }
    });
}

To retrieve the SPTrack from the SPPlaylistItem I use the SPSession's trackForURL method. In this method's callback I add the track to an array. This is where the problem is: adding these objects in the main thread is causing a bit of a lag. So my question is:

1. Is this the proper way of retrieving all the SPTrack objects inside an SPPlaylist? If not, what is the correct way to do this on a background thread so that my UI isn't blocked?

Any help is appreciated thank you!

Answer 1

Creating a new track via the URL is incredibly inefficient — the SPPlaylistItem contains the track itself.

Replace the part where you get the track by URL with something like this and you should be fine:

for (SPPlaylistItem *item in playlist.items) {
    if (item.itemClass == [SPTrack class])
        [mutableArray addObject:item.item];
}

Also, it's worth noting that fetching all of the tracks from a playlist at once is a fairly bad idea — playlists get very large, and holding onto 10,000 tracks when you've only got 20 or so onscreen at once is going to make you run out of memory fairly quickly.