Question

我用视频和“视频清单”表格,如YouTube,使用Django。

Now, I m making a "Video" and "Course(this is a video list)" table. I want to add one video to some different lists and search by both list and video, so let Course table have ManyToMany field link to Video table.

But in this way, I have some difficulty in videos order in a list. To display videos in the order I registered and to fix them anytime after, ManyToMany field must have something like "id" when it is registered, right?

I m a beginner of both Python and Django, so there may be some typical way... Any good ways to deal with this?

Answer 1

你们通过创建自己的中间模式(而不是使用Django所创造的暗中模式)来做到这一点:

class Video(models.Model):
    ...

class Course(models.Model):
    ...
    videos = models.ManyToManyField(Video, through= CourseVideo , related_name= courses )

class CourseVideo(models.Model):
    class Meta:
        ordering = [ order ]

    course = models.ForeignKey(Course)
    video = models.ForeignKey(Video)
    order = models.PositiveIntegerField(default=0)

The important part above is the through attribute on the ManyToManyField. This tells Django to use the CourseVideo model you defined instead of its own implicit version.

However, there s a few gotchas when you do this. You can no longer use things like some_course.videos.add(video), because additional information is needed now to create that relationship. Instead, you need to create the relationship explicitly:

CourseVideo.objects.create(course=some_course, video=some_video, order=1)

See the documentation for more details: https://docs.djangoproject.com/en/dev/topics/db/models/#intermediary-manytomany

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