django model on_delete pass self to models.SET()

Question

For example, I have a Book model, each book has its author and tag.

def get_authors_first_tag(book):
    try:
        tag = book.author.tags.first()
    except:         


        

Answer 1

The SET() doesn't accept any arguments, so you should use the signal receiver:

from django.db.models.signals.pre_delete
from django.dispatch import receiver

@receiver(pre_delete, sender=Tag)
def reset_tag(sender, **kwargs):
    tag = kwargs['instance']
    for book in books.filter(tag=tag):
        book.tag = book.author.tags.first()
        book.save()

Put this code into your models.py or make sure the file you put the receiver into is imported at the startup, so that the receiver is actually connected.