title: dispatch_async timeout method call
body: <p>Is there a good way to call an external method after a set time limit for completing the long process outlined below?  I would like the long process to stop trying after a set interval and call a method to try something else and wrap up the request.</p>
  
  <pre><code>dispatch_async(dispatch_get_global_queue(0, 0), ^{
  
      //// LONG PROCESS
  
      dispatch_async(dispatch_get_main_queue(), ^{
  
          //// RESULTS PROCESS
  
      });
  });
  </code></pre>