postgresql - 多对多关系中的查询集

Question

在这个项目中，我们为类里面的学生分配了徽章。

class Badge(models.Model):
    klass = models.ForeignKey( # klass means classroom
        'klass.Class',
        on_delete=models.CASCADE,
        related_name='badges',
        db_index=True,
    )
    users = models.ManyToManyField( # the students in 'klass' that have this badge
        User,
        through='UserBadge',
        through_fields=('badge', 'user'),
    )

users ManyToMany 字段的自定义中间表:

class UserBadge(models.Model):
    user = models.ForeignKey(
        User,
        on_delete=models.CASCADE,
        related_name='taken_badges',
    )
    badge = models.ForeignKey(
        Badge,
        on_delete=models.CASCADE,
        related_name='assigned_badges',
    )
        klass = models.ForeignKey( # this classroom is badge.klass
        'klass.Class',
        on_delete=models.CASCADE,
        related_name='assigned_badges',
    )

我需要找到与特定 user 和 klass 相关的所有徽章。这样我就可以检索特定教室中特定学生的所有徽章。

我试过了:

Bagde.objects.filter(userbadge__user__id = student_id,userbadge__klass__id=klass_id)

错误是:无法将关键字“userbadge”解析为字段。谢谢。

Answer 1

由于您已将 related_name 设置为 'assigned_badges'，因此您应该将过滤器实现为:

Bagde.objects.filter(
    <b>assigned_badges</b>__user__id=student_id,
    <b>assigned_badges</b>__klass__id=klass_id
)