Django，保存前创建新的外键(下拉列表)值

from django.db import models

class Author(models.Model):
    name = models.CharField(max_length=100)

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.ForeignKey(Author, on_delete=models.CASCADE)

from django.db import models

class Author(models.Model):
    name = models.CharField(max_length=100)

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.ForeignKey(Author, on_delete=models.CASCADE)

    def save(self, *args, **kwargs):
        if not self.author:
            new_author = Author.objects.create(name="New Author")
            self.author = new_author
        super().save(*args, **kwargs)