Monkey patching attributes to the instances would not be the correct
django idiom for adding a calculated field. There is a simple and
straight forward django idiom for expressing calculated fields in the
model.
In your car model, create a method named 'comment' returning the
required information:
def comment(self):
# ... do your calculations here
return # your calculated result here
Now just go to town accessing it just like a field when you need it.
You can even decorate it with additional information, such as
help_text or short_description to make it even more 'fieldy'.
See:
http://docs.djangoproject.com/en/dev/topics/db/models/#id3
On Sep 6, 3:33 am, Alex Chun <[EMAIL PROTECTED]> wrote:
> Thanks, Bruno. I will try that first thing Monday.
>
> Thanks for helping this newbie out!!
>
> On Sep 5, 5:50 pm, bruno desthuilliers <[EMAIL PROTECTED]>
> wrote:
>
> > On 6 sep, 02:19, Alex Chun <[EMAIL PROTECTED]> wrote:
>
> > > Thank you for the response. I should have said: the subclass is not
> > > part of the model, and thus is not reflected in database tables.
> > > I declare the subclass in one of my view functions. Without getting
> > > into the particulars of my app, I am trying to display a "list of
> > > cars" on a web page, along with some calculated information for each
> > > "car," which I have called the "comment" field.
>
> > You don't need subclassing nor models.fields to do so. Just add the
> > attribute(s) to your Car instances in the view. Here a simple example
> > in the interactive shell with the User class :
>
> > >>> from django.contrib.auth.models import User
> > >>> User.objects.all()
> > [<User: bruno>]
> > >>> u = _[0]
> > >>> u.some_data = "data"
> > >>> u.some_data
> > 'data'- Hide quoted text -
>
> > - Show quoted text -
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