title: How to Call the json webservice in the background?
body: <p>I have an application in which I have a settings page, where I need to edit each entity.  For that when the user selects each entity we will go to a separate page and edit there and come back.  I need to update the edited value by calling the service in background, but I need to come back to main view as soon as I edit the value.  So I am using the GCD way.</p>
  
  <pre><code>dispatch_async(backgroundQueue_, ^{
              [self update];
              dispatch_sync(dispatch_get_main_queue(), ^{
  
              });
          });
  </code></pre>
  
  <p>But sometimes I get the crashes like <code>ASHTTPheaders</code> <code>didreciveresponseheaders</code>,and <code>ASHTTprequest reportFailure</code>.  Can anybody point me in the right direction to achieve this.</p>