title: How to reduce boilerplate in responseJSON just like I use URLRequestConvertible to group related web calls
body: <p>I use URLRequestConvertible to groups my web calls, and to reduce the boilerplate code. But in each responseJSON I still have boilerplate to process my JSON response. They all look like these,</p>
  
  <ol>
  <li>Check response.result.isSuccess</li>
  <li>Check response.result.value as? the type data I expect (mostly a dictionary)</li>
  <li>Check for the success indicator in dictionary</li>
  <li>If succeed then retrieve the data I need.</li>
  </ol>
  
  <p>And because I group the related calls in one URLRequestConvertible, their responses have the similar format that I actually have the 5th step to further retrieve the "real" data I am looking for.</p>
  
  <p>So is there any way to reduce these boilerplate codes in responseJSON?</p>
  
  <p>BTW, I actually come up with a kludge solution for it. But I was wondering is there any common practice for that?</p>