如何在Django中正确使用auto_created属性? [英] How to correctly use auto_created attribute in django?

问题描述

我需要创建自己的中间模型.

I need to create my own intermediate model.

class class1(models.Model)

class class2(models.Model):
    field1 = models.ManyToManyField(class1, through="class3")

class class3(models.Model):
    field1 = models.ForeignKey(class1)
    field2 = models.ForeignKey(class2)
    field3 = models.IntegerField()

    class Meta:
        auto_created = True

我使用"auto_created = True"，因为在以下代码中，我出现了错误:

I use "auto_created=True" because in the following code, I had the error :

AttributeError:无法在用于指定中介模型的ManyToManyField上使用add().

AttributeError: Cannot use add() on a ManyToManyField which specifies an intermediary model.

for m2m_field in self._meta.many_to_many:
    for m2m_link in getattr(self, m2m_field.get_attname()).all():
        getattr(to_object, m2m_field.get_attname()).add(m2m_link)

现在它可以正常工作，但是当我尝试进行makemigration时，django希望删除我的class3(中间类)，并删除class2中field1中的通过"属性.

Now it works fine, but when I try to do a makemigration, django wants to remove my class3 (the intermediate class), and removing the "through" attribute in the field1 in class2.

我做错了什么?有解决方案吗?

What am I doing wrong ? Any solutions ?

全部.

推荐答案

据我所知，Meta类中的auto_created属性是未记录的，因此应避免使用它.

As far as I am aware, the auto_created attribute in the Meta class is undocumented, so you should avoid using it.

正如AttributeError所说，不可能将add()用于使用中介模型的多对多字段.正确的解决方法是创建中间模型的实例，而不是使用add().

As the AttributeError says, it is not possible to use add() for a many to many field that uses an intermediary model. The correct fix is to create an instance of the intermediate model, instead of using add().

class3.objects.create(field_1=c1, field_2=c2, field_3=1).

请参见

See the docs on extra fields in many to many relationships for more info.

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