title: iOS RestKit artificial identification attributes
body: <p>linked <a href="https://github.com/RestKit/RestKit/issues/1604" rel="nofollow">RestKit issue #1604</a></p>
  
  <p>If my API gives me no <code>id</code> attribute, but i still want to cache the objects via Core Data, what should i use to identify my object.
  For example i have</p>
  
  <pre><code>response =  {
    translation =     {
            text = "longlongtext";
            dictionary = "general";
            lang = "en";
        };
    otherdata =     {
            author = "May";
            date = "434134";
        };
  }
  </code></pre>
  
  <p>So i would be glad to use hashed (md5) translation text as an id string.
  Notice that my future requests which happen without network connection should be able to identify this cached entity and give it as a result.</p>
  
  <p>I cant declare mapping to fill <code>responseID</code> property from <code>[translation.text md5hash]</code> to use as <code>responseMapping.identificationAttributes = @[ responseID ];</code> because mappings doesnt have such feature.</p>