django之manytomanyfield

#mezzanine中BlogPost类的定义
class BlogPost(Displayable, Ownable, RichText, AdminThumbMixin):
    """
    A blog post.
    """

    categories = models.ManyToManyField("BlogCategory",#多对多，在BlogPost实例中不会出现
                                        verbose_name=_("Categories"),
                                        blank=True, related_name="blogposts")
    allow_comments = models.BooleanField(verbose_name=_("Allow comments"),
                                         default=True)
    comments = CommentsField(verbose_name=_("Comments"))
    rating = RatingField(verbose_name=_("Rating"))
    featured_image = FileField(verbose_name=_("Featured Image"),
        upload_to=upload_to("blog.BlogPost.featured_image", "blog"),
        format="Image", max_length=255, null=True, blank=True)
    related_posts = models.ManyToManyField("self",#相关的评论
                                 verbose_name=_("Related posts"), blank=True)

    admin_thumb_field = "featured_image"

该类会额外生成两个表：blogpost_categories和blogpost_related_posts