Question

I’d like to be able to save data submitted by the form based on an argument passed via the url that references the product (instead of having the user to specify the product through a dropdown). Any thoughts on how I can accomplish this?

url(r'^products/(?P<product_id>\d+)/reviews/$', 'view_reviews'),
url(r'^products/(?P<product_id>\d+)/add_review/$', 'add_review'), 

def add_review(request, product_id):
    p = get_object_or_404(Productbackup, pk=product_id)
    if request.method == 'POST':
        form = ReviewbackupForm(request.POST)
        if form.is_valid():
            form.save()
            return HttpResponseRedirect(reverse('reserve.views.view_reviews', kwargs={'product_id':p.id}))
    else:
        form = ReviewbackupForm()
    variables = RequestContext(request, {'form': form, 'product_id': product_id})
    return render_to_response('reserve/templates/create_review.html', variables)

RATING_OPTIONS = (
    (1, '1'),
    (2, '2'),
    (3, '3'),
    (4, '4'),
    (5, '5'),
    (6, '6'),
    (7, '7'),
    (8, '8'),
    (9, '9'),
    (10, '10'),
)
class Reviewbackup(models.Model):
    review = models.CharField('Review', max_length = 2000)
    date = models.DateField('date')
    created_on = models.DateTimeField(auto_now_add = True)
    updated_at = models.DateTimeField(auto_now = True)
    user = models.CharField('Username', max_length =  200)
    rating = models.IntegerField(max_length=2, choices=RATING_OPTIONS)
    product = models.ForeignKey(Productbackup)
    def __unicode__(self):
        return self.review

class ReviewbackupForm(ModelForm):
    class Meta:
        model = Reviewbackup
        fields = ('review', 'rating', 'user', 'date')
        widgets = {
            'review': Textarea(attrs={'cols': 80, 'rows': 7}),
        }

class Productbackup(models.Model):
    website = models.CharField('Product name', max_length = 200)
    website_url = models.URLField('Product URL')
    category = models.ForeignKey(Categories)
    created_on = models.DateTimeField(auto_now_add = True)
    updated_at = models.DateTimeField(auto_now = True)
    def __unicode__(self):
        return self.website

Answer 1

You can make use of form.save(commit=False), and set other attributes of your model in the instance and save it again.

In your view, when you save the form:

if form.is_valid():
    review = form.save(commit=False)
    review.product = p
    review.save()