title: NSManagedObject to JSON
body: <p>I have an entity class called catObras, and it inherits from the class NSManagedObject. What I want to do is pass it trough a web service (POST) in JSON form. If I sent the object I receive this:</p>
  
  <pre><code>&lt;catObras: 0x6d879f0&gt; (entity: catObras; id: 0x6d859b0 &lt;x-coredata://41B60B06-248C-488D-A14C-894E04D0395F/catObras/p2&gt; ; data: {
  Reporte = "&lt;relationship fault: 0x6d9dc40 'Reporte'&gt;";
  calendarioVisitas = "&lt;relationship fault: 0x6dac2c0 'calendarioVisitas'&gt;";
  catFondosInversion = "&lt;relationship fault: 0x6d7a1b0 'catFondosInversion'&gt;";
  contratista = nil;
  contrato = "XX-AYTO-ENS-BC-HABITAT-2011-IS-01";
  descripcion = "AMPLIACION DE RED DE DRENAJE SANITARIO COL. VISTA HERMOSA";
  direccion = nil;
  estatus = nil;
  fechaAprobacion = "2012-01-01 08:00:00 +0000";
  fechaInicio = "2012-01-31 08:00:00 +0000";
  fechaTerminacion = "2012-03-10 08:00:00 +0000";
  fechaUltimoRep = nil;
  idAgrupacion = 0;
  idObra = 5;
  inversionAprobada = 0;
  inversionAutorizada = 1668000;
  inversionContratada = 834000;
  nota = asdasdasdasda;
  numeroControl = "";
  obraPartidas = "&lt;relationship fault: 0x6d7a1f0 'obraPartidas'&gt;";
  observaciones = "muestras 2";
  oficioAprobacion = "SDS/122/11/1857 OF.001";
  supervisor = nil;})
  </code></pre>
  
  <p>I would like to pass this information in json form. Right now I'm using SBJSON (aka JSON-framework). When I try to use JSONRepresentation, it sends me this: </p>
  
  <blockquote>
    <p>JSONRepresentation failed. Error is: Not valid type for JSON</p>
  </blockquote>
  
  <p>Any suggestions?</p>