Django - 创建具有循环关系的模型 - 从实例到另一个实例？

Question

我目前正在做一个小项目。有两个模型很有趣：

-仓库

-仓库转移之间

注意：每个仓库都有多个不同型号的物品（即产品）；

问题：我希望能够将物品从一个仓库转移到另一个仓库。为此，在 BetweenWarehouseTransfers 中，我希望有一个字段指定我将说话物品转移到的仓库（to_warehouse），以及一个指定该物品来自哪个仓库的字段（from_warehouse）。稍后我想将 autocomplete_fields 添加到这两个仅接受现有仓库作为输入的字段。

有没有人知道如何创建这种循环关系。

我已经发布了几个我设想的解决方案，但每次都会出现循环关系问题：

#0。 （原版）

from django.db import models
from django_extensions.db.models import TimeStampedModel

# from supply_chain.models.warehouse import Warehouse


class WarehouseTransferProductVariant(TimeStampedModel):

    product_variant = models.IntegerField()
    amount = models.IntegerField()

    to_warehouse_id = models.CharField(blank=False, max_length=255)
    from_warehouse_id = models.CharField(blank=False, max_length=255)

    StatusChoices = models.TextChoices(
        "StatusChoices", "SENTREQUEST ACCEPTED DECLINED CANCELLED"
    )

    status = models.CharField(blank=True, choices=StatusChoices.choices, max_length=255)

    # relation_from_to = models.ManyToManyField('warehouse.Warehouse', related_name="fromwarehouse_towarehouse")

class FromWarehouseTransferProductVariant(TimeStampedModel):
    warehouse = models.ForeignKey(Warehouse, on_delete=models.RESTRICT)
    from_warehouse = models.CharField(max_length=255)

class ToWarehouseTransferProductVariant(TimeStampedModel):
    warehouse = models.ForeignKey(Warehouse, on_delete=models.RESTRICT)
    to_warehouse = models.CharField(max_length=255)

    productvarariant = models.IntegerField()
    amount = models.IntegerField()


    StatusChoices = models.TextChoices(
        "StatusChoices", "SENTREQUEST ACCEPTED DECLINED CANCELLED"
    )

    status = models.CharField(blank=True, choices=StatusChoices.choices, max_length=255)

class WarehouseTransferProductVariant(TimeStampedModel):
    productvarariant = models.IntegerField()
    amount = models.IntegerField()

    to_warehouse = models.CharField(blank=False, max_length= 255)
    from_warehouse = models.CharField(blank=False, max_length= 255)

    StatusChoices = models.TextChoices(
        "StatusChoices", "SENTREQUEST ACCEPTED DECLINED CANCELLED"
    )

    status = models.CharField(blank=True, choices=StatusChoices.choices, max_length=255)


    to_warehouse_id = models.ForeignKey(Warehouse)
    from_warehouse_id = models.ForeignKey(Warehouse)
    type_of_relation = models.SmallPositiveIntegerField(choices=[(1,'from'), (2, 'to')])

提前致谢。

Answer 1

这就是我会做的：

class WarehouseTransferProduct(TimeStampedModel):
    product = models.ForeignKey('Product')
    to_warehouse = models.ForeignKey('Warehouse', related_name='to_warehouse')
    from_warehouse = models.ForeignKey('Warehouse', related_name='from_warehouse')
    amount = models.IntegerField()

    StatusChoices = models.TextChoices(
        "StatusChoices", "SENT REQUEST ACCEPTED DECLINED CANCELLED"
    ) #look https://stackoverflow.com/questions/18676156/how-to-properly-use-the-choices-field-option-in-django for status

    status = models.CharField(blank=True, choices=StatusChoices.choices, max_length=255)

Answer 2

我学会了在 Django 中避免循环导入/关系的 1 个技巧是

无论何时使用models.ForeignKey()，都写成

models.ForeignKey('appname.modelname', related_name="related_name_of_your_pref")

或

models.ForeignKey('modelname', related_name="related_name_of_your_pref")

如果两个模型在同一个models.py