多对多关系中的对象的存在

Question

Python Django 代码：

class UserGroup(models.Model):
    users = models.ManyToManyField(User)

    def __contains__(user):
        pass # What should be here?

(User这里是另一个模型。)

如何高效地检查一个用户"belongs"是否属于给定的用户组？

Answer 1

可以通过m2m manager查看：

def __contains__(self, user):
    return user in self.users.all() # return boolean

现在用你的实例检查一下：

user = User.objects.get(pk=some_pk) 
group = UserGroup.objects.get(pk=some_pk)
# or use another queries to fetch instanses
if user in group:
    # do your logic

多对多关系中的对象的存在

Existence of an object in many-to-many relation

django

many-to-many

model

django-models