'View on site' link gives error

Using Django Mystery Errors
1

Hi, I’m following the MDN Django tutorial and noticed an issue. I’m using Django 4.1.5 with Python 3.10.6. Per that tutorial, I added a ‘get_absolute_url’ method to the Book model like this:

class Book:
    ...
    def get_absolute_url(self):
        """Returns the URL to access a detail record for thid book"""
        return reverse('book-detail', args=[str(self.id)])

Doing this caused “View on Site” button to appear next to “History” on the Admin Book edit page as expected. When I hover over the button, I see the url: http://127.0.0.1:8000/admin/r/10/2/ If I click the button, I get the following error:

NoReverseMatch at /admin/r/10/2/

Reverse for 'book-detail' not found. 'book-detail' is not a valid view function or pattern name.

Request Method: 	GET
Request URL: 	http://127.0.0.1:8000/admin/r/10/2/
Django Version: 	4.1.5
Exception Type: 	NoReverseMatch
Exception Value: 	

Reverse for 'book-detail' not found. 'book-detail' is not a valid view function or pattern name.

Exception Location: 	/home/dow/django/venv1/lib/python3.10/site-packages/django/urls/resolvers.py, line 828, in _reverse_with_prefix
Raised during: 	django.contrib.contenttypes.views.shortcut
Python Executable: 	/home/dow/django/venv1/bin/python3
Python Version: 	3.10.6
Python Path: 	

['/home/dow/django/locallibrary',
 '/home/dow/ngsuite/ngsolve-install/lib/python3/dist-packages',
 '/home/dow/django',
 '/home/dow/django/locallibrary',
 '/usr/lib/python310.zip',
 '/usr/lib/python3.10',
 '/usr/lib/python3.10/lib-dynload',
 '/home/dow/django/venv1/lib/python3.10/site-packages']

Server time: 	Fri, 20 Jan 2023 08:54:40 -0800

I haven’t made any customizations to the admin templates. Also, I tried changing the function to use kwargs and ‘pk’ as in the Django documentation:

    def get_absolute_url(self):
        """Returns the URL to access a detail record for thid book"""
        return reverse('book-detail', kwargs={'pk' : self.pk})

but that gave the same error. Thanks for any help on this, and please let me know if a full stack trace would help.

2

We would need to see your urls.py file. Also identify whether that urls.py file is your root urls.py file or a file in an application being referenced by your root urls.py file. (The “root urls.py” file is the file identified in your settings.py file.)

3

Thanks, Ken! Here are the contents of the root urls.py file:

from django.conf import settings
from django.conf.urls.static import static
from django.contrib import admin
from django.urls import include, path
from django.views.generic import RedirectView

# just for development, serve static files.
urlpatterns = [
    path('admin/', admin.site.urls),
    path('catalog/', include('catalog.urls')),
    path('', RedirectView.as_view(url='catalog/', permanent=True)),
] + static(settings.STATIC_URL, document_root=settings.STATIC_ROOT)

The application urls.py is currently empty, since this tutorial begins with building the model and playing with the admin pages.

4

That’s the cause of your error - you’re looking for a url named ‘book-detail’, but you don’t have that url defined yet.

1 Like
5

Ok – thanks! I assumed that generating the book-detail url and corresponding view/template was a function of the admin application. I probably just didn’t read far enough ahead in the tutorial…