Question

I have an iPhone app which is pulling just about all it’s data from ASP.NET MVC services.

Basically just returning JSON.

When I run the app in the simulator, the data is pulled down very fast etc.. however when I use the actual device (3G or WiFi) it’s extremely slow. To the point that the app crashes for taking too long.

a) Should I not be calling a service from the FinishedLaunching method in AppDelegate?

b) Am I calling the service incorrectly?

The method I’m using goes something like this:

public static JsonValue GetJsonFromURL(string url) {
     var request = (HttpWebRequest)WebRequest.Create (url);
     request.AutomaticDecompression = DecompressionMethods.GZip |     DecompressionMethods.Deflate;
     using(var response = (HttpWebResponse)request.GetResponse()) {
          using(var streamReader = new StreamReader(response.GetResponseStream())) {
                 return JsonValue.Load(streamReader);
          }
     }
}

Is there a better or quicker way I should be querying a service? I’ve read about doing things on different threads or performing async calls to not lock the UI, but I’m not sure what the best approach or how that code would work.

Answer 1

a) Should I not be calling a service from the FinishedLaunching method in AppDelegate?

You get limited time to get your application up and running, i.e. returning from FinishedLaunching or the iOS watchdog will kill your application. That’s about 17 seconds total (but could vary between devices/iOS versions).

Anything that takes some time is better done in another thread, launched from FinishedLaunching. It’s even more important if you use networking services as you cannot be sure how much time (or even if) you’ll get an answer.

b) Am I calling the service incorrectly?

That looks fine. However remember that the simulator has a faster access to the network (likely), much more RAM and CPU power. Large data set can take a lot of memory / CPU time to decode.

Running from another thread will, at least, cover the extra time required. It can be as simple as adding the code (below) inside your FinishedLaunching.

ThreadPool.QueueUserWorkItem (delegate {
    window.BeginInvokeOnMainThread (delegate {
        // run your code
    });
});

You can have a look at how Touch.Unit does it by looking at its TouchRunner.cs source file.

note: you might want to test not using (asking) for compressed data since the time/memory to decompress it might not be helpful on devices (compared to the simulator). Actual testing needed to confirm 😉