python Django 多对多关系，并通过
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Django many-to-many relations, and through
提问by Jiaaro
I want to store which user invited another user to a group... but django is telling me this is ambigous and against the rules (which makes sense).
我想存储哪个用户邀请另一个用户加入一个组......但 django 告诉我这是模棱两可的并且违反规则（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.
groups.group：中介模型Group_to_Member 有多个外键给User，这是不明确的，是不允许的。
So how do I do this correctly? Maybe a generic relation? might work but seems a bit convoluted... Here's how I was approaching it (with unrelated bits removed)
那么我该如何正确地做到这一点呢？也许是泛型关系？可能有用，但似乎有点复杂……这是我的处理方式（删除了无关的部分）
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")
Solution
解决方案
Ok so I did a little combination of the answers you guys provided (Thanks!) and things I found on the internet plus my own admittedly meager python-fu:
好的，所以我结合了你们提供的答案（谢谢！）和我在互联网上找到的东西以及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")
采纳答案by Graham King
You have to manage it yourself:
您必须自己管理：
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')
Then instead of group.members.all()you do group.membership_set.all().
然后代替group.members.all()你做group.membership_set.all()。
Also, I wouldn't use 'Group' as your model name, as Django already has a Group object.
另外，我不会使用“Group”作为模型名称，因为 Django 已经有一个 Group 对象。
回答by Mauricio Abreu
It is possible if you are using Django 1.7.
如果您使用的是 Django 1.7，这是可能的。
From the docs: https://docs.djangoproject.com/en/1.7/topics/db/models/#extra-fields-on-many-to-many-relationships
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.
在 Django 1.6 及更早版本中，包含多个外键的中间模型曾经被禁止用于多对多关系中涉及的任何模型。
