Question

I’m looping through a list of dates and making a request to a web server for each date in the list.

I would like each date to be processed completely before the subsequent request is sent to the server. To do this, I have set up a serial dispatch queue using GCD. Each time through the date loop, a block is added to the queue.

The problem I am having is that my NSURLConnection is set up using the standard asynchronous call. This results in requests not blocking any subsequent requests. They are thus overrunning each other.

My question: Is this a case where it would make sense for me to use the synchronous NSURLConnection (within the dispatch queue) or is there some other way to make it work using the standard asynchronous call?

Answer 1

There are number of ways to do this. Whatever method you choose, starting the connection needs to be tied to completion of your processing task.

1. In each block you add to your serial queue, use a synchronous request. This is probably the quickest solution given your current implementation as long as you’re ok with the limited error handling of a synchronous request.

2. Don’t use a serial queue. Start the first asynchronous connection and process the response. When processing is complete start the next asynchronous connection. Rinse and repeat.