How to make order?

Question

Django

class Doc(models.Model):
  name_doc = models.CharField("Название", max_length=150, null=True, blank=True)
  files = models.FileField("Документы", upload_to = "product/documents/", null=True, blank=True)
  doc_format = models.ForeignKey(Format, verbose_name='Формат файла', on_delete=models.DO_NOTHING, null=True, blank=True)
  demo = models.ManyToManyField(Demo, verbose_name="Демо", on_delete=models.DO_NOTHING, null=True, blank=True)


  def __str__(self):
    return f'{self.name_video} - {self.name_doc}'

  class Meta:
    verbose_name = 'Видео и документ'
    verbose_name_plural = "Видео и документы"


class Demo(models.Model):
  name = models.CharField("номер стрваницы", max_length=150)
  demo_img = models.ImageField("Демо изображение", upload_to="product/documents/demo/")
  page_number = models.IntegerField()
  doc = models.ForeignKey(Doc, verbose_name="файлы демо", on_delete=models.CASCADE)

  def __str__(self):
    return f'{self.name} - {self.doc}'
  class Meta:
    verbose_name = 'Демо просмотр'
    verbose_name_plural = "Демо просмотр"

I need the ManyToMany (From Doc) field to take data from Demo, and the foreignkey (Demo) field to take the document name from Doc

Answer 1

When such a desire arises, it is more like a design problem. Why is the doc field needed for Demo?
ZY even not so:
demo as ManyToManyField at Doc, it is necessary only if the same demo can be in several Docs, if it is not so, then doc as ForeignKey at Demo is enough.