django.urls.exceptions.NoReverseMatch: Reverse for 'publisher_edit' with arguments '(None,)' not found. 1 pattern(s) tried: ['books/publishers/(?P<p_id>[0-9]+)/$']

[melission]

Hi,
In Chapter07/Exercise7.03/bookr/reviews/views.py I met a problem, namely I got an exception as updated_publisher doesn't have an id ('pk' in this book). My code:
views.py

 if request.method == 'POST':
        form = PublisherForm(request.POST, instance=publisher)
        if form.is_valid():
            updated_publisher = form.save()
            if publisher is None:
                messages.success(request, f'Publisher {updated_publisher} was created.')
            else:
                messages.success(request, f'Publisher {updated_publisher} was updated.')  
          
            return redirect("publisher_edit", updated_publisher.id)

forms.py

class PublisherForm(forms.ModelForm):
    class Meta:
        model = Publisher
        fields = '__all__'

models.py

class Publisher(models.Model):
    id = models.IntegerField(primary_key=True, editable=False)
    name = models.CharField(max_length=64)
    website = models.URLField(help_text="Publisher's website", blank=True)

    def __str__(self):
        return self.name

Yet, if I get a database object and return redirect based on it (the last line of the code), everything works as was intended.

if request.method == 'POST':
        form = PublisherForm(request.POST, instance=publisher)
        if form.is_valid():
            updated_publisher = form.save()
            # get a database obj
            pub = Publisher.objects.get(name=updated_publisher.name)
            if publisher is None:
                messages.success(request, f'Publisher {updated_publisher} was created.')
            else:
                messages.success(request, f'Publisher {updated_publisher} was updated.')  
            # pub - a database obj
            return redirect("publisher_edit", pub.id)

Though there is another problem. If I have more than one Publisher with the same name and try Publisher.objects.get(), I get an error as .get() can retrieve only one object.

I don't know whether the authors are reading issues, yet if they are, it would be nice to get a piece of advice or an explanation how I can get an id value ('pk' in this book).

Thanks!

[beneboy]

Check your Publisher model. In Django, you don't need to specify the id field as it's created automatically. It should be like this.

class Publisher(models.Model):
    """A company that publishes books."""
    name = models.CharField(max_length=50,
                            help_text="The name of the Publisher.")
    website = models.URLField(help_text="The Publisher's website.")
    email = models.EmailField(help_text="The Publisher's email address.")

    def __str__(self):
        return self.name

Everything else looks fine. You can check out the final bookr code for Chapter 7 here: https://github.com/PacktPublishing/Web-Development-with-Django/tree/master/Chapter07/final/bookr and compare it with what you have.

Though there is another problem. If I have more than one Publisher with the same name and try Publisher.objects.get(), I get an error as .get() can retrieve only one object.

That's to be expected, the get() method is designed to retrieve exactly one object.