Re: How can I control JSON serialization?

Here's a simple copy-paste from some code I wrote yesterday. I'm not sure it's The Right Way of doing things, but it gets the job done.

Assume a model Customer with fields id, name and email.

  # views.py from django.utils import simplejson from django.views.generic.list import ListView

  def customer_serialize(queryset):     if isinstance(queryset[0], Customer):         result = []         last_find = 0         for customer in queryset:             result += [dict(id=customer.id, name=customer.name, email=customer.email), ]         return result     else:         raise TypeError(repr(queryset) + " is not JSON serializable or isn't a valid Customer queryset.")

  class CustomerSearch(ListView):     model = Customer     slug_field = 'email'     context_object_name = 'customers'     template_name = 'customer/index.html'          def get_queryset(self):         self.queryset = self.model.objects.filter(email__startswith=self.kwargs['slug'])         return self.queryset              def get(self, context, **kwargs):         # the important bits         if self.request.is_ajax():             result = customer_serialize(self.get_queryset())             return HttpResponse(                             simplejson.dumps(result),                             mimetype='application/json',                             )                      return super(CustomerSearch, self).get(context, **kwargs) 

I hope that helps! My code is a little different, in reality, so forgive me for any typos as I didn't really test this.

Sincerely,

Andre Terra

On Sat, Feb 26, 2011 at 6:30 PM, Alexander Bolotnov <abolotnov@gmail.com> wrote:

Is there a way to control json serialization in django? Simple code below will return serialized object in json:

  co = Collection.objects.all()
  c = serializers.serialize('json',co)
  

The json will look similar to this:

  [
      {
          "pk": 1,
          "model": "picviewer.collection",
          "fields": {
              "urlName": "architecture",
              "name": "\u0413\u043e\u0440\u043e\u0434 \u0438 \u0430\u0440\u0445\u0438\u0442\u0435\u043a\u0442\u0443\u0440\u0430",
              "sortOrder": 0
          }
      },
      {
          "pk": 2,
          "model": "picviewer.collection",
          "fields": {
              "urlName": "nature",
              "name": "\u041f\u0440\u0438\u0440\u043e\u0434\u0430",
              "sortOrder": 1
          }
      },
      {
          "pk": 3,
          "model": "picviewer.collection",
          "fields": {
              "urlName": "objects",
              "name": "\u041e\u0431\u044a\u0435\u043a\u0442\u044b \u0438 \u043d\u0430\u0442\u044e\u0440\u043c\u043e\u0440\u0442",
              "sortOrder": 2
          }
      }
  ]
  

You can see it's serializing it in a way that you are able to re-create the whole model, shall you want to do this at some point - fair enough, but not very handy for simple JS ajax in my case: I want bring the traffic to minimum and make the whole thing little clearer.

What I did is I created a view that passes the object to a .json template and the template will do something like this to generate "nicer" json output:

  [
  {% if collections %}
      {% for c in collections %}
  {"id": {{c.id}},"sortOrder": {{c.sortOrder}},"name": "{{c.name}}","urlName": "{{c.urlName}}"}{% if not forloop.last %},{% endif %}
      {% endfor %}
  {% endif %}
  ]
  

This does work and the output is much (?) nicer:

  [
      {
          "id": 1,
          "sortOrder": 0,
          "name": "Город и архитектура",
          "urlName": "architecture"
      },
      {
          "id": 2,
          "sortOrder": 1,
          "name": "Природа",
          "urlName": "nature"
      },
      {
          "id": 3,
          "sortOrder": 2,
          "name": "Объекты и натюрморт",
          "urlName": "objects"
      } 
  ]
  

However, I'm bothered by the fast that my solution uses templates (an extra step in processing and possible performance impact) and it will take manual work to maintain shall I update the model, for example.

I'm thinking json generating should be part of the model (correct me if I'm wrong) and done with either native python-json and django implementation but can't figure how to make it strip the bits that I don't want.

One more thing - even when I restrict it to a set of fields to serialize, it will keep the id always outside the element container and instead present it as "pk" outside of it.

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