Question

I wrote an __init__ method for one of my models that adds some auxiliary information to the object by dynamically adding an attribute to the object that does not reflect a column in the database:

class MyModel(models.Model):
    title = Models.CharField()
    description = Models.TextField()

    def __init__(self, *args, **kwargs):
        self.aux_info = "I'm not in the database!"

This seemed to be working fine, but I found a case where it does not work. I have some code in a view where I set a status variable and package up a list of MyModels into json like so:

from django.core import serializers 
from django.utils import simplejson 

...

# have to use serializers for django models
serialized_items = serializers.serialize("json", itemlist)
data["items"] = serialized_items # serialized_items is now a string
data["status"] = status

# package up data dict using simplejson for python objects
resp = simplejson.dumps(data)
return HttpResponse(resp, mimetype="application/javascript")

The problem seems to be that django’s serializers only serialize the model fields and not all attributes of the object so aux_info does not come through. I’m also pretty sure that using both serializers and simplejson is not the right way to do this. Thanks for any help!

Answer 1

Try usung the serialiser’s optional fields argument.

serialized_items = serializers.serialize("json", itemlist, fields=['.....', 'aux_info'])

May i also suggest that using the __init__ method to add fields is considdered bad form in django and would be much better achieved like so:

class MyModel(models.Model):
    title = Models.CharField()
    description = Models.TextField()

    def aux_info(self):
        return "I'm not in the database!"