Django多对多关系，并通过

Question

我想存储邀请其他用户加入组的用户。。。但django告诉我这是矛盾的，违反了规则（这是有道理的）。

groups.group: Intermediary model Group_to_Member has more than one foreign key to User, which is ambiguous and is not permitted.

那我该怎么做呢？可能是一般关系？可能有用，但似乎有点复杂。。。下面是我如何接近它（去掉无关的部分）

from django.contrib.auth.models import User

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

class UserGroup_to_Member(models.Model):
    group = models.ForeignKey(UserGroup)
    member = models.ForeignKey(User)

    invited_by = models.ForeignKey(User, related_name="group_invited_users")

解决方案

好吧，我把你们提供的答案结合起来了（谢谢！）我在网上找到的东西，加上我自己公认的微薄的python fu：

from django.contrib.auth.models import User

class UserGroup(models.Model):
    # notice there is no member object here
    ... other model data

    def add_member(self, **kwargs):
        g2m = UserGroup_to_Member(group = self,  **kwargs)
        g2m.save()

    def remove_member(self, member):
        g2m = UserGroup_to_Member.objects.get(group=self, member=member)
        g2m.delete()

    # This is not elegant at all, help please? I'm pretty sure it isn't
    # as bad on the database as it looks though.
    def get_members(self):
        g2ms = UserGroup_to_Member.objects.filter(group=self)
        member_ids = [g2m.member.id for g2m in g2ms]
        members = User.objects.none()
        for id in member_ids:
            members = members | User.objects.get(id=id)
        return members

class UserGroup_to_Member(models.Model):
    group = models.ForeignKey(UserGroup)
    member = models.ForeignKey(User)

    invited_by = models.ForeignKey(User, related_name="group_invited_users")

Answer 1

你必须自己管理：

class MyGroup(models.Model):
    name = models.CharField(max_length=100)

class Membership(models.Model):
    group = models.ForeignKey(MyGroup)
    member = models.ForeignKey(User)

    invited_by = models.ForeignKey(User, related_name='invited_set')

然后你就不用group.members.all()而是group.membership_set.all()。

另外，我不会使用'Group'作为模型名，因为Django已经有了一个Group对象。

Answer 2

如果您使用的是Django 1.7，那么这是可能的。

来自文档：https://docs.djangoproject.com/en/1.7/topics/db/models/#extra-fields-on-many-to-many-relationships

In Django 1.6 and earlier, intermediate models containing more than one foreign key to any of the models involved in the many-to-many relationship used to be prohibited.