通过中间模型，该模型具有两个多个关系

Question

我有一个模型，它有两个独立的ManyToManyField关系

class Company(models.Model):
    parent          =     models.ManyToManyField("self", through='CompanyParent', through_fields=('company_child', 'company_parent'), related_name='+')
    child           =     models.ManyToManyField("self", through='CompanyParent', through_fields=('company_parent', 'company_child'), related_name='+')

上述方法在本地主机Django v3.0.2/SQLite 3.8.7.2上运行良好

为了真正发布它，我不得不使用Django v2.1.15/SQLite 3.7.17，但是发布的版本中出现了以下错误

companies.Company.child: (fields.E332) Many-to-many fields with intermediate tables must not be symmetrical.

companies.Company.parent: (fields.E332) Many-to-many fields with intermediate tables must not be symmetrical.

companies.Company: (models.E003) The model has two many-to-many relations through the intermediate model 'companies.CompanyParent'.

这是怎么回事？通过向每个模型添加symmetrical=False解决了前两个问题，但不知道如何解决最终错误

Answer 1

您可以选中this answer设置两个多对多关系

上述答案中的一个例子：

class Person(models.Model): 
    name = models.CharField(max_length=127, blank=False)
    to_users = models.ManyToManyField(
        'self', 
        symmetrical=False, 
        related_name='from_users',
        through='Event', 
        through_fields=('from_user', 'to_user'),
    )

class Event(models.Model):
    item = models.ForeignKey(Item, related_name='events')
    from_user = models.ForeignKey(Person, related_name='events_as_giver')
    to_user = models.ForeignKey(Person, related_name='events_as_receiver')