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POPerforming network and other time consuming tasks in background
 

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    <p>I'm developing a network based iOS app that downloads json data from the server and processes it. Both the downloading task and processing task can take a significant time to complete, So I don't want to perform either on the main thread.</p> <p>I think there are 2 ways to do this:</p> <ol> <li><p>Perform asynchronous loading using <code>NSURLConnection</code> and in the <code>didFinishLoading</code> method use <strong>GCD</strong> (say) to do the processing in background.</p></li> <li><p>Use <strong>GCD's</strong> <code>dispatch_async</code> (say) to start work in background and use <code>NSURLConnection's</code> <code>sendSynchronousRequest:returningResponse:error</code> to download the data synchronously, Do the processing of the data, And call <code>UI</code> updates on the main thread.</p></li> </ol> <p>I think the 2nd method would be easier to write and would produce cleaner code, Especially if one "download/process data" task involves multiple sequential service calls for data download. So rather than execution going like:</p> <p><strong>main (start) -> background (download) -> main (<code>NSURLConnectionDelegate</code> method) -> background (data processing) -> main (<code>UI</code> update</strong>)</p> <p>We would have:</p> <p><strong>main (start) -> background (download) -> background (data processing) -> main (UI update) which seems to be cleaner to me.</strong></p> <p>I found 2 similar questions: <a href="https://stackoverflow.com/questions/6591416/good-pattern-for-internet-requests-with-grand-central-dispatch">Good pattern for Internet requests with Grand Central Dispatch?</a> And<br> <a href="https://stackoverflow.com/questions/5037545/nsurlconnection-and-grand-central-dispatch">NSURLConnection and grand central dispatch</a></p> <p>And the answers to both seem to suggest using something conceptually similar to method 1.</p> <p>Is there no proper way to achieve what's described in method 2?</p> <p>Thanks in advance!</p>
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    1. COHave a look at [AFNetworking](https://github.com/AFNetworking/AFNetworking).
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      1. USMike D
    2. CO@MikeD, What AFNetworking can additionally do here is performing the JSON parsing in background, isn't it? What if I need to perform expensive processing on the parsed JSON objects? I think what I'm looking for is more of a design pattern than a framework :)
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    3. COI am always using second approach but one advantage with first approach is prior to ios 6 if you want to timeout post request with less than 240 secs, its possible by canceling asynchronous connection.
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