python - Django ORM Annotate bool 字段定义了团队的用户成员

Question

models.py

from django.db import models


class UserGroup(models.Model):
    members = models.ManyToManyField(User, related_name='members', through='UserGroupMember')


class UserGroupMember(models.Model):
    user = models.ForeignKey(User)
    usergroup = models.ForeignKey(UserGroup)


class Cohort(models.Model):
    user_groups = models.ManyToManyField(UserGroup)


class Team(models.Model):
    cohort = models.ForeignKey(Cohort)
    members = models.ManyToManyField(User, related_name='team_members', through='TeamMembers', blank=True)


class TeamMembers(models.Model):
    team = models.ForeignKey(Team)
    user = models.ForeignKey(User)

单个用户只能属于同一群组中的一个团队。

我想注释新字段( bool 值)，它告诉您是分配给群组中某个团队的用户，例如:

User.objects.filter(
    members__cohort=cohort
).annotate(
    is_team_member=...
)

<小时/>

我使用的是 Python 2.7.13 和 Django 1.9.8。谢谢。

Answer 1

我通过加入Cohort模型并使用条件表达式成功解决了这个问题:

from django.db.models import Case, When, Value, IntegerField


users = User.objects.filter(
    members__cohort=cohort
).annotate(
    is_team_member=Case(When(team_members__cohort=cohort, then=Value(1)), default=0, output_field=IntegerField())
)

现在我可以轻松过滤，例如，属于某个团队的用户:

users.filter(is_team_member=1)