Background network calls - iOS

I've started using NSOperationQueue in my own work lately, for controlling background network requests. NSOperation deals with most of the boilerplate code necessary for asynchronously running tasks (such as network operations) on threads in the background (or foreground, if necessary for UI updates).

It also allows dependencies across queues; for example, I use two queues in my application:

The first schedules image downloads, at a max concurrency of 2 at a time, in the background. Each image download has a corresponding completion handler (as an NSBlockOperation) that is dependent on the image download completing. These operations sit on the [NSOperationQueue mainQueue], which operates on the main thread, allowing them to update UI (specifically, the corresponding UIImageView).

Note that NSOperation and NSOperationQueue are not for network requests only, but any operation that can be divided into atomic tasks and scheduled concurrently.

Here are Apple's intro docs on the topic.

Having implemented something similar myself, I would recommend using a service and not a thread to do network calls. That way even if your activity gets killed you're sure your network calls will be executed.

Then to implement the queue i suggest you take a look into IntentService (http://developer.android.com/reference/android/app/IntentService.html)

from the docs:

IntentService is a base class for Services that handle asynchronous requests (expressed as Intents) on demand. Clients send requests through startService(Intent) calls; the service is started as needed, handles each Intent in turn using a worker thread, and stops itself when it runs out of work.

This "work queue processor" pattern is commonly used to offload tasks from an application's main thread. The IntentService class exists to simplify this pattern and take care of the mechanics. To use it, extend IntentService and implement onHandleIntent(Intent). IntentService will receive the Intents, launch a worker thread, and stop the service as appropriate.

All requests are handled on a single worker thread -- they may take as long as necessary (and will not block the application's main loop), but only one request will be processed at a time.

If your application is simple enough you can use sendBroadCast() to share info and notifications between your activity and the IntentService