我有三种模型,用户,成就和用户成就:
class User(AbstractUser):
email = models.EmailField(_('email address'), unique=True)
...
class Achievement(models.Model):
name = models.CharField(max_length=64)
points = models.PositiveIntegerField(default=1)
class UserAchievement(models.Model):
# Use a lazy reference to avoid circular import issues
user = models.ForeignKey('users.User', on_delete=models.CASCADE)
achievement = models.ForeignKey(Achievement, on_delete=models.CASCADE)
我想用“点数”列注释用户,该列总结了UserAchievement表中列出的所有成就所获得的总点数。
但是很明显,我并没有完全了解注释的工作方式。当我尝试时:
users = User.objects.annotate(points=Sum('userachievement__achievement__points'))
for u in users:
print(u.email, u.points)
它崩溃与:
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "/Users/dylan/.local/share/virtualenvs/server-E23dvZwD/lib/python3.7/site-packages/django/db/models/query.py", line 274, in __iter__
self._fetch_all()
File "/Users/dylan/.local/share/virtualenvs/server-E23dvZwD/lib/python3.7/site-packages/django/db/models/query.py", line 1242, in _fetch_all
self._result_cache = list(self._iterable_class(self))
File "/Users/dylan/.local/share/virtualenvs/server-E23dvZwD/lib/python3.7/site-packages/django/db/models/query.py", line 78, in __iter__
setattr(obj, attr_name, row[col_pos])
AttributeError: can't set attribute
答案 0 :(得分:1)
您可以使用User
作为通过表的Achievement
至UserAchievement
之间的ManyToManyField,以简化查询
class User(AbstractUser):
email = models.EmailField(_('email address'), unique=True)
achievements = models.ManyToManyField('Achievement', through='UserAchievement')
...
这可以用于注释
User.objects.annotate(points=Sum('achievements__points'))
如果您有一个用户实例
user.achievements.all()
对于错误,我相信您在用户模型上有一个名为points的属性