使用django-notifications时如何修复'on_delete'位置参数缺失错误？

Looks like you're hitting a compatibility snag between your Django version and the older django-notifications package. Let's break down why this happens and how to fix it quickly:

Why the Error Occurs #

Starting with Django 2.0, the ForeignKey field requires an explicit on_delete parameter to define what happens when the related object is deleted (e.g., cascade delete, block deletion, etc.). The version of django-notifications you're using was built for older Django versions and doesn't include this mandatory parameter in its model code—hence the TypeError pointing to line 170 of notifications/models.py.

Solution 1: Upgrade to a Compatible Package (Recommended) #

The original django-notifications package is no longer actively maintained. Instead, use the community-supported fork django-notifications-redux, which supports Django 2.0+ and includes the required on_delete parameters out of the box:

1. Uninstall the outdated package:

   pip uninstall django-notifications
   

2. Install the updated fork:

   pip install django-notifications-redux
   

3. Double-check your INSTALLED_APPS in settings.py still includes 'notifications' (the app name stays the same for the fork):

   INSTALLED_APPS = [
       # ... your other apps
       'notifications',
   ]
   

4. Run migrations to sync the database schema with the updated model:

   python manage.py migrate
   

Solution 2: Manually Patch the Old Package (Not Recommended) #

If you absolutely need to stick with the original django-notifications package, you can manually add the on_delete parameter to the problematic line. Note that this change will be overwritten if you update the package later:

1. Open the file referenced in the error: C:\Python36\lib\site-packages\notifications\models.py
2. Locate line 170, which looks like this:

   recipient = models.ForeignKey(settings.AUTH_USER_MODEL, blank=False, related_name='notifications')
   

3. Add the on_delete=models.CASCADE parameter (you can pick other options like PROTECT or SET_NULL based on your needs):

   recipient = models.ForeignKey(settings.AUTH_USER_MODEL, blank=False, related_name='notifications', on_delete=models.CASCADE)
   

4. Save the file and restart your Django server.

Quick Notes on on_delete Options #

• models.CASCADE: Delete the notification when the related user is deleted (most common use case)
• models.PROTECT: Block deleting the user if there are linked notifications
• models.SET_NULL: Set the recipient field to NULL (requires adding null=True to the field definition)

内容的提问来源于stack exchange，提问作者paula moreno gutierrez