title: RestKit - saving JSON content into a string coredata attribute
body: <p>I need to parse a JSON web service response containing a key whose children are not known.</p>
  
  <p>For example let's have the following JSON response where the keys of the customData attribute are defined at runtime:</p>
  
  <pre><code>{
      "score": 996,
      "customData": { "key1": "key1value", "key2": "key2value" },
      "isRegistered": true,
      "allowOpening": "OK"
  }
  </code></pre>
  
  <p>Would it be possible to save the JSON content of customData into a string coredata attribute?</p>
  
  <p>I've tried with a simple mapping like this:</p>
  
  <pre><code>RKEntityMapping *mapping = [RKEntityMapping mappingForEntityForName:[[self class] description] inManagedObjectStore:managedObjectStore];
  [mapping addAttributeMappingsFromDictionary:@{
                   @"score": @"score",
                   @"customData":@"customData",
                   @"isRegistered":  @"isRegistered",
                   @"allowOpening": @"allowOpening"}];
  </code></pre>
  
  <p>but it doesn't work, customData saved by coredata is always empty.</p>
  
  <p>Many thanks,
  DAN</p>