class JSONField(models.TextField): 
  __metaclass__ = models.SubfieldBase 
  description = "Json" 
  def to_python(self, value): 
    v = models.TextField.to_python(self, value) 
    try: 
      return json.loads(v)['v'] 
    except: 
      pass 
    return v 
  def get_prep_value(self, value): 
    return json.dumps({'v':value}) 

class Category(models.Model): 
  name = fields.MedialNameField() 
  other= fields.JSONField()