Django List 删除当前对象将被删除的对象

Question

在我的 DeleteView 模板中，我想警告用户删除当前对象将删除以下对象(因为数据库架构需要 on_delete = models.CASCADE)。

这是一个示例模型:

class Book(models.Model):
    course = models.ForeignKey(Course, related_name = 'course_books', on_delete = models.CASCADE, null = True, blank = True)

class Exercise(models.Model):
    book = models.ForeignKey(Book, related_name = 'exercises', on_delete = models.CASCADE, null = True, blank = True)
    ...

class Solution(models.Model):
    exercise = models.ForeignKey(Exercise, related_name = 'solutions', on_delete = models.CASCADE, null = True, blank = True)

因此，假设用户要删除一门类(class)，我想警告用户在删除当前书籍时将删除哪些书籍、练习和解决方案。一些这样的效果:

WARNING: Deleting course Programming 101 will delete Python Programming for Beginners and Python By Example.  It will also delete Excersises 1-5 and solutions 1-10

这将要求我可以查看相关字段以查看 on_delete 是否设置为 CASCADE。如果是，我应该将它添加到 to_be_deleted 对象列表中。

我查看了是否可以检查该字段的 on_delete 属性:

for related_object in the_course._meta.related_objects:
    dir(related_object.field)

但没有任何帮助，所以我在这里伸出手...

Answer 1

你可以这样做

from django.contrib.admin.utils import NestedObjects
from django.db import DEFAULT_DB_ALIAS

collector = NestedObjects(using=DEFAULT_DB_ALIAS)
collector.collect([obj])
print(collector.nested())