blocks|key|1100255|text|在the+docs中查看ManyToManyField的symmetrical选项--听起来它可以做您想做的事情。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1100256|对于具体的操作方式，我会这样做|1100257|class+LameUserExtension(User):
++++friends+=+ManyToManyField("self",+through=Friendship)

class+Friendship(models.Model):
++++#+the+stuff+you+had+here|code-block|syntax|javascript|1100258|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.djangoproject.com/en/dev/ref/models/fields/#manytomanyfield^0|C|F|S|B|1|8|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|F|3|G|5|6|7|12|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|13|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

Check out the <code>symmetrical</code> option of <code>ManyToManyField</code> in <a href="http://docs.djangoproject.com/en/dev/ref/models/fields/#manytomanyfield" rel="noreferrer">the docs</a> -- sounds like it can do what you want.

For the specific way you're doing it, I'd do something like

<pre><code>class LameUserExtension(User):
 friends = ManyToManyField("self", through=Friendship)

class Friendship(models.Model):
 # the stuff you had here
</code></pre>

blocks|key|1100343|text|我发现了一篇很好的文章，讨论了一段时间以前，基础知识如下：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1100344|class+Person(models.Model):
++++name+=+models.CharField(max_length=100)
++++relationships+=+models.ManyToManyField('self',+through='Relationship',+
+++++++++++++++++++++++++++++++++++++++++++symmetrical=False,+
+++++++++++++++++++++++++++++++++++++++++++related_name='related_to%2B')

RELATIONSHIP_FOLLOWING+=+1
RELATIONSHIP_BLOCKED+=+2
RELATIONSHIP_STATUSES+=+(
++++(RELATIONSHIP_FOLLOWING,+'Following'),
++++(RELATIONSHIP_BLOCKED,+'Blocked'),
)

class+Relationship(models.Model):
++++from_person+=+models.ForeignKey(Person,+related_name='from_people')
++++to_person+=+models.ForeignKey(Person,+related_name='to_people')
++++status+=+models.IntegerField(choices=RELATIONSHIP_STATUSES)|code-block|syntax|javascript|1100345|请注意related_name末尾的加号。这向Django表明不应该暴露反向关系。因为关系是对称的，所以这是期望的行为，毕竟，如果我是A的朋友，那么A也是我的朋友。Django不会为您创建对称关系，因此需要向add_relationship和remove_relationship方法添加一点内容，以显式地处理关系的另一面：|1100346|def+add_relationship(self,+person,+status,+symm=True):
++++relationship,+created+=+Relationship.objects.get_or_create(
++++++++from_person=self,
++++++++to_person=person,
++++++++status=status)
++++if+symm:
++++++++#+avoid+recursion+by+passing+`symm=False`
++++++++person.add_relationship(self,+status,+False)
++++return+relationship

def+remove_relationship(self,+person,+status,+symm=True):
++++Relationship.objects.filter(
++++++++from_person=self,+
++++++++to_person=person,
++++++++status=status).delete()
++++if+symm:
++++++++#+avoid+recursion+by+passing+`symm=False`
++++++++person.remove_relationship(self,+status,+False)|1100347|现在，每当我们创建一个单向的关系时，它的补充就会被创建(或删除)。由于关系是双向的，我们可以简单地使用：|1100348|def+get_relationships(self,+status):
++++return+self.relationships.filter(
++++++++to_people__status=status,+
++++++++to_people__from_person=self)|1100349|来源：Self-referencing+many-to-many+through|offset|length|1100350|entityMap|0|LINK|mutability|MUTABLE|url|https://charlesleifer.com/blog/self-referencing-many-many-through/^0|0|0|0|0|0|0|3|11|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|15|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|16|8|@]|9|@$Q|17|R|18|1|19]]|A|$]]|$1|S|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

I found a nice article discussing that some time ago, the basics are the following:

<pre><code>class Person(models.Model):
 name = models.CharField(max_length=100)
 relationships = models.ManyToManyField('self', through='Relationship', 
 symmetrical=False, 
 related_name='related_to+')

RELATIONSHIP_FOLLOWING = 1
RELATIONSHIP_BLOCKED = 2
RELATIONSHIP_STATUSES = (
 (RELATIONSHIP_FOLLOWING, 'Following'),
 (RELATIONSHIP_BLOCKED, 'Blocked'),
)

class Relationship(models.Model):
 from_person = models.ForeignKey(Person, related_name='from_people')
 to_person = models.ForeignKey(Person, related_name='to_people')
 status = models.IntegerField(choices=RELATIONSHIP_STATUSES)
</code></pre>

Note the plus-sign at the end of related_name. This indicates to Django that the reverse relationship should not be exposed. Since the relationships are symmetrical, this is the desired behavior, after all, if I am friends with person A, then person A is friends with me. Django won't create the symmetrical relationships for you, so a bit needs to get added to the add_relationship and remove_relationship methods to explicitly handle the other side of the relationship:

<pre><code>def add_relationship(self, person, status, symm=True):
 relationship, created = Relationship.objects.get_or_create(
 from_person=self,
 to_person=person,
 status=status)
 if symm:
 # avoid recursion by passing `symm=False`
 person.add_relationship(self, status, False)
 return relationship

def remove_relationship(self, person, status, symm=True):
 Relationship.objects.filter(
 from_person=self, 
 to_person=person,
 status=status).delete()
 if symm:
 # avoid recursion by passing `symm=False`
 person.remove_relationship(self, status, False)
</code></pre>

Now, whenever we create a relationship going one way, its complement is created (or removed). Since the relationships go in both directions, we can simply use:

<pre><code>def get_relationships(self, status):
 return self.relationships.filter(
 to_people__status=status, 
 to_people__from_person=self)
</code></pre>

Source: <a href="https://charlesleifer.com/blog/self-referencing-many-many-through/" rel="nofollow">Self-referencing many-to-many through</a>

Let's use the classic example of friends.

<pre><code>class Friendship(models.Model):
 user1 = models.ForeignKey(User, related_name='friends1')
 user2 = models.ForeignKey(User, related_name='friends2')
 handshakes = models.PositiveIntegerField()
 hugs = models.PositiveIntegerField()
 # other silly data
</code></pre>

Two friends in a friendship (user1 and user2) should be completely equal. I should be able to say that (user1, user2) are unique_together and not have to worry about (user2, user1) accidentally showing up. I should be able to get all the friends of a given user easily, but instead I'd have to write a custom manager or create some other way of getting all the Friendships where that user is user1 in the relationship, and all the Friendships where that user is user2.

I'm considering trying to write my own SymmetricKey. Someone please stop me.

How do I model a symmetric relationship with django?

Django

让我们使用朋友的经典例子。class Friendship(models.Model):    user1 = models.ForeignKey(User, related_name='friends1')    user2 = models.ForeignKey(User, related_name='friend...

问如何建模与django的对称关系？
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