Question

I have the following model in a project:

class CarAssignment(models.Model):
    leg = models.ForeignKey(Leg, null=True, blank=True)
    driver = models.ForeignKey(Driver, null=True, blank=True)
    riders = models.ManyToManyField(Rider, null=True, blank=True)

I’m trying to create a page with a table where an admin user can edit the driver and riders items for all of the car assignments in a specific group. I can’t use a formset because I also need to add data from another model, and because the choices in each list come from a different subset of riders and drivers, those that belong to a specific group. Driver is a select list and Riders is a multiselect list.

I have successfully built the page and table to represent the data, with correctly working drop-down lists. However, I can’t figure out how to save the items. Here’s a specific problem scenario:

for row 1 in the table (representing CarAssignment object #1), I pick a new driver from the list in the select dropdown. I’m assigning custom name tags in the html to identify them, as follows:

<option selected name="select.driver.{{ car_assignment.id }}">{{ driver }}</option>

Then in the view, I’m trying to see if it matches anything, as follows:

        for car_assignment in CarAssignment.objects.filter(leg__in=legs):
            driver_tag = "select.driver." + str(car_assignment.id)
            if driver_tag in request.POST:
                car_assignment.driver = driver
                car_assignment.save()

The problem is that when it finds a matching driver tag, all it returns is a string of the First Name and Last Name. I can’t do the car_assignment.driver = driver because it’s trying to equate a driver object to a string.

I’m not sure how to do this. I guess I could parse out the first and last names and try to match them against the Driver model to get the Driver objects I need, but that seems inefficient and possibly error-prone.

Any help is appreciated (I’m a programming and Django newbie). Thanks.

Answer 1

I’m not sure where your that driver field is coming from, but if it’s a String, you could then do another query to get the driver object like so:

for car_assignment in CarAssignment.objects.filter(leg__in=legs):
    driver_tag = "select.driver." + str(car_assignment.id)
    if driver_tag in request.POST:
        # Get the driver object
        driver = Driver.objects.filter(name=driver_name)[0]

        car_assignment.driver = driver
        car_assignment.save()

I’d also highly recommend that you read the Django tutorial Working with forms. The logic that you’re writing in the view should be moved to a form object. Your view can then instantiate the form and pass the post data. The form can then be validated and will handle saving your new objects. This is the best way to do this.

The updated flow for your view would be simplified to something like this:

def my_view(request):
    if request.method == 'POST':
        form = MyForm(request.POST)
        if form.is_valid():
            form.save()

            # Do something here like redirect the user
            # to acknowledge that the form was submitted successfully.
    else:
        form =  MyForm()

    return render_to_response('form.html', {
        'form': form,
    })

By passing the form to your template you can generate the form doing nothing but this:

{{ form.as_ul }}