在将Django项目移植到Python 3和Django 2时迁移问题 [英] Migrating problems when porting Django project to Python 3 and Django 2

问题描述

我一直在将Django项目移植到Python 3和Django2。我必须按照Django 2的要求，使用外键将on_delete添加到我的所有模型中。现在，我已尝试进行这些更改的迁移 TypeError：__init __（）缺少1个必需的位置参数：'on_delete'。

I've been porting a Django project to Python 3 and Django 2. I have had to add on_delete to all my models with foreign keys as required in Django 2. Now I have tried to make migrations for those changes have been getting TypeError: __init__() missing 1 required positional argument: 'on_delete'.

其引用的文件为0002迁移文件，而不是已更新的模型文件。我不确定如何解决此问题。我尝试伪造迁移，但仍然遇到相同的错误。

The file it references is the 0002 migration file not the models file which has been updated. I am not sure how to go about fixing this. I have tried faking the migrations and I still get the same error.

我不确定为什么它认为数据库不存在，我已经检查过并且一切都完好无损在Postgres工作。有想法吗？

I am not sure why it thinks the database doesn't exist, I have checked and everything is intact and working in Postgres. Any ideas?

推荐答案

因为 django-2.0 ForeignKey 字段[Django-doc] 和 OneToOneField 字段字段现在具有必需的 on_delete 参数。

Since django-2.0 ForeignKey fields [Django-doc] and OneToOneField fields fields now have a required on_delete parameter.

在在 2.0中删除的功能下的Django-2.0发行说明 ：

ForeignKey on_delete 参数在模型和迁移中，现在需要是c $ c>和 OneToOneField 。考虑压缩迁移，以便您减少更新。

The on_delete argument for ForeignKey and OneToOneField is now required in models and migrations. Consider squashing migrations so that you have fewer of them to update.

因此，您应该检查迁移文件中的 ForeignKey s和 OneToOneField s，并添加 on_delete 参数，例如：

You thus should inspect your migration files for ForeignKeys and OneToOneFields, and add an on_delete parameter, like:

class Migration(migrations.Migration):

    initial = False

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

    operations = [
        migrations.CreateModel(
            name='Model',
            fields=[
                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('some_foreignkey', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='app.OtherModel')),
            ],
        ),
    ]

您应检查关于 on_delete 参数的文档以查看哪种删除策略最适合每种情况在撰写本文时，这些选项包括 CASCADE ， PROTECT ， SET_NULL ， SET_DEFAULT ， SET（..），不要做什么。

You should inspect the documentation on the on_delete parameter to see what deletion strategy is the best for each situation. The options are, at the time of writing CASCADE, PROTECT, SET_NULL, SET_DEFAULT, SET(..), DO_NOTHING.

如果您未在on_delete agged / django-2.0 class = post-tag title =显示已标记'django-2.0'的问题 rel = tag> django-2.0 版本，它默认设置为 CASCADE 。因此，如果您想要相同的行为，则应添加 on_delete = models.CASCADE 。在 1.11版本中对此进行了说明 on_delete 上的文档：

If you did not specify the on_delete in the pre-django-2.0 versions, it made a default to CASCADE. So if you want the same behavior, you should add on_delete=models.CASCADE. This is noted in the 1.11 version of the documentation on on_delete:

从1.9版开始不推荐使用： on_delete将成为Django 2.0中的必需参数。在旧版本中，默认值为 CASCADE 。

Deprecated since version 1.9: on_delete will become a required argument in Django 2.0. In older versions it defaults to CASCADE.

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