python - 如何在抽象模型的 ManyToMany 字段中设置 related_name？

Question

我有这个抽象模型:

class HasSystemMessage(models.Model):
    class Meta:
        abstract = True

    messages = models.ManyToManyField(SystemMessage, related_name=?)

我打算在至少三个其他模型中使用这个抽象模型，比方说 A、B 和 C。如何为这些类动态设置 related_name？例如，对于 B 类，我希望 related_name 为 Bs。有可能吗？

为了进一步澄清问题，类将如下所示:

class B(HasSystemMessage):
    # Some model fields 
class A(HasSystemMessage):
    # Some model fields

HasSystemMessage.objects.filter(a__contains=[some elements])

Answer 1

您可以使用 %(class)s 或 %(app_label)s

class HasSystemMessage(models.Model):
    class Meta:
        abstract = True

    messages = models.ManyToManyField(SystemMessage, related_name=%(app_label)s_%(class)s_related)

来自 Django 文档

Be careful with related_name and related_query_name¶ If you are using related_name or related_query_name on a ForeignKey or ManyToManyField, you must always specify a unique reverse name and query name for the field. This would normally cause a problem in abstract base classes, since the fields on this class are included into each of the child classes, with exactly the same values for the attributes (including related_name and related_query_name) each time.

To work around this problem, when you are using related_name or related_query_name in an abstract base class (only), part of the value should contain '%(app_label)s' and '%(class)s'.

'%(class)s' is replaced by the lower-cased name of the child class that the field is used in. '%(app_label)s' is replaced by the lower-cased name of the app the child class is contained within. Each installed application name must be unique and the model class names within each app must also be unique, therefore the resulting name will end up being different.

引用:https://docs.djangoproject.com/en/2.0/topics/db/models/#be-careful-with-related-name-and-related-query-name