Dajngo模型嵌入多个抽象模型

Question

假设我有一个用于在我的站点上存储客户订单的Order模型。将有两个地址字段：shipping_address和billing_address。我可以写成这样：

class Order(models.Model):
  order_number = models.CharField()
  time_created = models.DateTimeField()
  ...
  shipping_name = models.CharField()
  shipping_city = models.CharField()
  shipping_street = models.CharField()
  shipping_building = models.CharField()
  billing_name = models.CharField()
  billing_city = models.CharField()
  billing_street = models.CharField()
  billing_building = models.CharField()
  ...

然后通过order.shipping_name和order.billing_name访问字段，但是当每个地址都需要包含15-20个字段时，这会变得非常麻烦。

我尝试了一对一的关系，但是应用程序的其他地方的代码变得非常复杂。

如果只有一个地址字段，我可以使用抽象模型来使其变得更清晰：

class Address(models.Model):
  class Meta:
    abstract = True
  name = models.CharField()
  city = models.CharField()
  street = models.CharField()
  building = models.CharField()
  ...

class Order(Address, models.Model):
  order_number = models.CharField()
  time_created = models.DateTimeField()

但是这样，我只能拥有一组地址数据，Address类中的字段名将与来自Order的字段发生冲突。

是否有一种方法将具有给定前缀的字段注入或嵌入到给定模型中？我正在寻找类似于Spring模型中使用的@Embedded装饰器的东西。

我会想象它看起来是这样的：

class Address(models.Model):
  class Meta:
    abstract = True
  name = models.CharField()
  city = models.CharField()
  street = models.CharField()
  building = models.CharField()
  ...

class Order(models.Model):
  order_number = models.CharField()
  time_created = models.DateTimeField()
  shipping_address = Embedded(Address, prefix='shipping')
  billing_address = Embedded(Address, prefix='billing')

然后通过order.shipping_address.city访问字段，或者不破坏其他地方的代码，也许order.shipping_address_city也能工作。

编辑:使用JSONField或HStoreField可以实现类似的功能吗？

Answer 1

经过大量的尝试和错误之后，使用来自https://stackoverflow.com/a/55051990/345811的模型工厂的方法似乎对我来说是最好的。

下面是示例models.py实现：

from django.db import models
from django.utils.translation import gettext_lazy as _

from app.countries import COUNTRIES  # A list of country code/name tuples

ADDRESS_FIELDS = (
    ('first_name', dict(verbose_name=_('First name'), max_length=256)),
    ('last_name', dict(verbose_name=_('Last name'), max_length=256)),
    ('company', dict(verbose_name=_('Company'), max_length=256, required=False)),
    ('street', dict(verbose_name=_('Street address'), max_length=256)),
    ('street2', dict(verbose_name=_('Street address line 2'), max_length=256, required=False)),
    ('street3', dict(verbose_name=_('Street address line 3'), max_length=256, required=False)),
    ('postal_code', dict(verbose_name=_('Postal code'), max_length=16)),
    ('city', dict(verbose_name=_('City'), max_length=64)),
    ('province', dict(verbose_name=_('Province'), max_length=64, required=False)),
    ('country', dict(verbose_name=_('Country'), choices=COUNTRIES, max_length=2)),
)


def address_model_factory(field_prefix, force_optional=False):
    """
    Usage:
    class SomeModel(address_model_factory(''), address_model_factory('billing', True))
    """
    class AbstractAddressModel(models.Model):
        class Meta:
            abstract = True

    for field_name, field_def in ADDRESS_FIELDS:
        required = field_def.get('required', True)
        field_kwargs = {k: v for k, v in field_def.items() if k != 'required'}
        if force_optional or not required:
            field_kwargs.update(blank=True, default="")
        AbstractAddressModel.add_to_class(field_name if not field_prefix else f'{field_prefix}_{field_name}',
                                          models.CharField(**field_kwargs)
                                          )

    return AbstractAddressModel


class Shipment(address_model_factory(''), address_model_factory('billing', True)):
    status = models.Charfield(_('Shipment status'), max_length=20)

会产生这样的迁移：

class Migration(migrations.Migration):

    initial = True

    operations = [
        migrations.CreateModel(
            name='Shipment',
            fields=[
                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('first_name', models.CharField(max_length=256, verbose_name='First name')),
                ('last_name', models.CharField(max_length=256, verbose_name='Last name')),
                ('company', models.CharField(blank=True, default='', max_length=256, verbose_name='Company')),
                ('street', models.CharField(max_length=256, verbose_name='Street address')),
                ('street2', models.CharField(blank=True, default='', max_length=256, verbose_name='Street address line 2')),
                ('street3', models.CharField(blank=True, default='', max_length=256, verbose_name='Street address line 3')),
                ('postal_code', models.CharField(max_length=16, verbose_name='Postal code')),
                ('city', models.CharField(max_length=64, verbose_name='City')),
                ('province', models.CharField(blank=True, default='', max_length=64, verbose_name='Province')),
                ('country', models.CharField(choices=[('DE', 'Germany'), ('GB', 'United Kingdom')], max_length=2, verbose_name='Country')),
                ('billing_first_name', models.CharField(blank=True, default='', max_length=256, verbose_name='First name')),
                ('billing_last_name', models.CharField(blank=True, default='', max_length=256, verbose_name='Last name')),
                ('billing_company', models.CharField(blank=True, default='', max_length=256, verbose_name='Company')),
                ('billing_street', models.CharField(blank=True, default='', max_length=256, verbose_name='Street address')),
                ('billing_street2', models.CharField(blank=True, default='', max_length=256, verbose_name='Street address line 2')),
                ('billing_street3', models.CharField(blank=True, default='', max_length=256, verbose_name='Street address line 3')),
                ('billing_postal_code', models.CharField(blank=True, default='', max_length=16, verbose_name='Postal code')),
                ('billing_city', models.CharField(blank=True, default='', max_length=64, verbose_name='City')),
                ('billing_province', models.CharField(blank=True, default='', max_length=64, verbose_name='Province')),
                ('billing_country', models.CharField(blank=True, choices=choices=[('DE', 'Germany'), ('GB', 'United Kingdom')], default='', max_length=2, verbose_name='Country')),
                ('status', models.CharField(max_length=20, verbose_name='Shipment status')),
            ],
            options={},
        ),
    ]

Answer 2

嵌入另一个模型的一部分作为引用可能是不可能的，而且，它肯定是非标准的方式。唯一推荐的解决方案是使用两种不同的模型：Order和Address。然后按顺序将地址指定为ForeignKey

class Order(models.Model):
    ...
    shipping_address = models.ForeignKey(
        Address, on_delete=models.SET_NULL, related_name="shipped_orders",
        blank=True, null=True
    )
    invoice_address = models.ForeignKey(
        Address, on_delete=models.SET_NULL, related_name="invoiced_orders",
        blank=True, null=True
    )

它将显示为一个选择框在管理，您可以选择发货和发票地址。为了使它更简单，只需在管理中使用字段即可。

如果您需要在管理页面中进行一些验证，同时添加一个订单，您可以设置一个将在管理页面中使用的模型，文档的这一部分描述了如何做到这一点。在您的自定义订单表单中，您可以验证像def clean_shipping_address(self)这样的字段，更详细地描述这里。