Django 反向关系与递归 M2M 关系

Question

尝试从此处的文档进行扩展：https://docs.djangoproject.com/en/1.10/topics/db/models/#extra-fields-on-many-to-many-relationships

上下文更容易理解，Person 对象，M2M 与自身的关系定义了两个 Person 之间的 'relationship types'，例如 Parent/Child/Engaged

我的Models.py：

RELATIONSHIPS = (

    (0, 'Child'),
    (1, 'Parent'),
    (2, 'Engaged'),
)

class Person(models.Model):
    code = models.AutoField(primary_key=True, verbose_name="Person Code")
    name = models.CharField(max_length=150, blank=True, null=True, verbose_name="Name")

    relationships = models.ManyToManyField(
        'self', 
        through = 'Person_Person', #This lets you define the model that will act as an intermadiary
        symmetrical = False, #This needs to be set with recursive relationships
        )

class Person_Person(models.Model):
    person_1 = models.ForeignKey('Person', on_delete=models.CASCADE, 
        related_name='%(class)s_person_1', verbose_name="Person 1")
    person_2 = models.ForeignKey('Person', on_delete=models.CASCADE,
        related_name='%(class)s_person_2', verbose_name="Person 2")
    relationship_type = models.IntegerField(choices = RELATIONSHIPS, default = 5, verbose_name="Relation")

测试代码：

p1 = Person.objects.create(name = 'Man')
p2 = Person.objects.create(name = 'Woman')

relation = Person_Person(person_1 = p1, person_2 = p2, relationship_type = 2)
reation.save()

print(p1.relationships.all(), p2.relationships.all())
#>><QuerySet [<Person: 108 Woman>]>
#>><QuerySet []>

现在的问题是，p2 的关系字段查询集返回空，我理解为什么当你考虑非递归关系时，但在这种情况下调用 p2.relationships_set 没有从某种意义上说，即使有，我怎么知道 Person 是关系的 person_1 还是 person_2？

欢迎任何建议

Answer 1

这似乎是 How to make recursive ManyToManyField relationships that have extra fields symmetrical in Django? 但我不能标记它们

基本上这在 django 中是不可能的，因为你必须定义 symmetrical=False。您可以选择以相反的方式添加第二个 m2m 字段。另一个线程对此有一些很好的读物

Django 反向关系与递归 M2M 关系

Django Reverse relationship with Recursive M2M Relationship

django

django-models

python-3.5

django-1.10