Question

创建从ForeignKey继承的自定义字段并设置to字段时，存在解构问题。

简化示例（models.py）

from django.db import models
from django.contrib.auth.models import User


class UserField(models.ForeignKey):

    def __init__(self, *args, **kwargs):
        kwargs['to'] = User
        super(UserField, self).__init__(*args, **kwargs)

    def deconstruct(self):
        name, path, args, kwargs = super(UserField, self).deconstruct()
        del kwargs['to']
        return name, path, args, kwargs


class FooBar(models.Model):
    user = UserField()

当python manage.py makemigrations引发以下异常时。

Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 377, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 338, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/makemigrations.py", line 111, in handle
    convert_apps=app_labels or None,
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/autodetector.py", line 40, in changes
    changes = self._detect_changes(convert_apps, graph)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/autodetector.py", line 139, in _detect_changes
    self.generate_renamed_models()
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/autodetector.py", line 413, in generate_renamed_models
    model_fields_def = self.only_relation_agnostic_fields(model_state.fields)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/autodetector.py", line 79, in only_relation_agnostic_fields
    del deconstruction[2]['to']
KeyError: u'to'

可以通过在解构过程中不删除'to'kwarg来解决，但是，这显然会在构造函数中留下不需要的'to'kwarg，如下所示：

from django.db import models, migrations
from django.conf import settings
import bar.models


class Migration(migrations.Migration):

    dependencies = [
        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
    ]

    operations = [
        migrations.CreateModel(
            name='FooBar',
            fields=[
                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                ('user', bar.models.UserField(to=settings.AUTH_USER_MODEL)),
            ],
            options={
            },
            bases=(models.Model,),
        ),
    ]

我已经尝试了一些变体（例如将User作为超级调用的第一个arg），但是，结果大致相同或产生其他问题。有没有更好/不同的方法来正确实现这样的自定义字段的迁移支持？

Django Custom Field继承ForeignKey deconstruct（）失败

0 个答案: