attributeError：＆＃x27; str＆＃x27;对象没有属性＆＃x27; _Meta＆＃x27;迁移

Question

我将库存模型移至自己的应用程序中，并重置所有迁移和数据库。 python manage.py makemigrations没有问题，但是迁移时我会遇到错误。希望有人可以将我指向一个方向，因为追溯似乎对我解决问题并不有帮助。

*由于堆栈溢出限制，我删除了代码的某些部分和追溯

django版本4.0.2

trackback

Operations to perform:
  Apply all migrations: admin, auth, contenttypes, inventory, item, project_site, requisition, sessions, transfer, users
Running migrations:
  Applying contenttypes.0001_initial... OK
  Applying contenttypes.0002_remove_content_type_name... OK
  Applying auth.0001_initial... OK
  ...
  Applying item.0001_initial... OK
  Applying project_site.0001_initial...Traceback (most recent call last):
  File "C:\Users\Bernard\pelicans\imrs-capstone\imrs\manage.py", line 22, in <module>
    main()
  File "C:\Users\Bernard\pelicans\imrs-capstone\imrs\manage.py", line 18, in main
    execute_from_command_line(sys.argv)
  File "C:\Users\Bernard\pelicans\imrs-capstone\env\lib\site-packages\django\core\management\__init__.py", line 
425, in execute_from_command_line
    utility.execute()
...
  File "C:\Users\Bernard\pelicans\imrs-capstone\env\lib\site-packages\django\db\migrations\operations\models.py", line 92, in database_forwards
    schema_editor.create_model(model)
  File "C:\Users\Bernard\pelicans\imrs-capstone\env\lib\site-packages\django\db\backends\base\schema.py", line 364, in create_model
    if field.remote_field.through._meta.auto_created:
AttributeError: 'str' object has no attribute '_meta'

project_site/migrations/migrations/0001_initial.py.py.py

from django.db import migrations, models


class Migration(migrations.Migration):

    initial = True

    dependencies = [
        ('item', '0001_initial'),
    ]

    operations = [
        migrations.CreateModel(
            name='Cart',
            fields=[
                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('cartItemCount', models.PositiveIntegerField(default=0)),
            ],
        ),
        migrations.CreateModel(
            name='Site',
            fields=[
                ...
                ('inventory_items', models.ManyToManyField(blank=True, related_name='inventory_items', through='inventory.Inventory', to='item.Item')),
                ('siteCart', models.ManyToManyField(blank=True, related_name='siteCart', through='project_site.Cart', to='item.Item')),
            ],
        ),
    ]

project_site/models.py.pypy.py

class Site(models.Model):
    siteCart = models.ManyToManyField(
        'item.Item',
        through='Cart',
        through_fields=('site', 'cartItem'),
        blank=True,
        related_name='siteCart')
    inventory_items = models.ManyToManyField(
        'item.Item',
        through='inventory.Inventory',
        through_fields=('site', 'item'),
        blank=True,
        related_name='inventory_items'
        )

库存/models.py

class Inventory(models.Model):
    item = models.ForeignKey('item.Item', on_delete=models.CASCADE)
    site = models.ForeignKey(Site, on_delete=models.CASCADE)
    ...

库存/迁移/0001_Initial.py

from django.db import migrations, models
import django.db.models.deletion


class Migration(migrations.Migration):

    initial = True

    dependencies = [
        ('item', '0001_initial'),
    ]

    operations = [
        migrations.CreateModel(
            name='Inventory',
            fields=[
                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('siteItemCount', models.PositiveIntegerField(default=0)),
                ('siteItemStatus', models.PositiveSmallIntegerField(choices=[(0, 'Above Threshold'), (1, 'Moderate'), (2, 'Low'), (3, 'Critical'), (4, 'Empty')], default=1)),
                ('siteItemTurnover', models.CharField(choices=[('S', 'Slow'), ('N', 'Normal'), ('F', 'Fast')], default='F', max_length=1)),
                ('siteItemMinThreshold', models.PositiveSmallIntegerField(default=0)),
                ('item', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='item.item')),
            ],
        ),
    ]

Answer 1

您有循环迁移依赖性的问题，project_site和库存相互取决于彼此。如果您希望保持当前的应用程序/模型结构，则需要将迁移文件分解，以便可以在没有循环依赖项的步骤中应用它们。

首先删除库存中引用模型中的模型的 site 模型迁移

project_site_site/migrations/0001_initial.py：

from django.db import migrations, models


class Migration(migrations.Migration):

    initial = True

    dependencies = [
        ('item', '0001_initial'),
    ]

    operations = [
        ...
        migrations.CreateModel(
            name='Site',
            fields=[
                ...
                # delete this line ('inventory_items', models.ManyToManyField(blank=True, related_name='inventory_items', through='inventory.Inventory', to='item.Item')),
            ],
        ),
    ]

然后添加初始

> project_site 迁移作为初始库存迁移库存/迁移/0001_initial.py

from django.db import migrations, models
import django.db.models.deletion


class Migration(migrations.Migration):

    initial = True

    dependencies = [
        ('item', '0001_initial'),
        ('project_site', '0001_initial'),
    ]

    ...

：然后在project_site中创建一个新的迁移添加> 应该可以使用这是可能的

Manytomanyfield ，现在

from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('project_site', '0001_initial'),
        ('inventory', '0001_initial'),
    ]

    operations = [
        migrations.AddField(
            model_name='Site',
            name='inventory_items',
            field=models.ManyToManyField(blank=True, related_name='inventory_items', through='inventory.Inventory', to='item.Item')
        )
    ]