pre_delete我正在嘗試為我的 Django 應(yīng)用程序模型使用信號Like。該Like模型有一個(gè)Book外鍵。該Book模型有一個(gè)num_of_likes字段。最終，我試圖num_of_likes從我的信號中更新這個(gè)字段pre_delete。只是我做不到。我的代碼會(huì)讓問題是什么變得非常清楚，我想（請?zhí)貏e注意注釋和打印語句）：書籍/模型.py：class Book(models.Model):    num_of_likes = models.IntegerField()喜歡/ models.py：class Like(models.Model):    user = models.ForeignKey(User)    book = models.ForeignKey(Book)喜歡/views.py：class DeleteLikeView(APIView):    def post(self, request, book):        book = get_object_or_404(Book, id=book)        print(book.num_of_likes) # Prints, say, 10        like = Like.objects.get(user=request.user, book=book)        like.delete() # triggers signal handler below (should update `book.num_of_likes`)        print(book.num_of_likes) # Still prints 10, expected 9 <------ PROBLEM        return ...喜歡/信號.py：@receiver(pre_delete, sender=Like)def delete_book_like(sender, instance, **kwargs):    print(instance.book.num_of_likes) # Prints 10    instance.book.num_of_likes -= 1    instance.book.save()    print(instance.book.num_of_likes) # Prints 9, as expected為什么book.num_of_likes內(nèi)部得到更新delete_book_like但更改卻沒有顯示在 中DeleteLikeView？