更新 Django 中的模型实例，使旧实例及其与其他实例的关系不受影响

Question

我一直在做一个电子商务项目。我有三个模型 Item、OrderItem、Order。它们与外键链接（项目 -> 订单项目 -> 订单）。 Item 是实际产品，订单包含 Item(s)。

Item基本上代表一个产品。在 Item 中有一个属性 'price' 需要根据需要更新。比如在促销或其他活动期间。

当我更新一个项目的价格时，该项目的价格也会在已经完成的订单实例中更新。

基本上我想以某种方式分离这些模型，这样 Item 模型中的任何更改都不会影响已完成的订单。

class Item(models.Model):
    title = models.CharField(max_length=100)
    sku = models.CharField(max_length=8, validators=[
                           MinLengthValidator(8)], unique=True)
    upc = models.CharField(max_length=12, validators=[
                           MinLengthValidator(12)], unique=True, blank=True, null=True)
    date_updated = models.DateTimeField(
        auto_now=True, blank=True, null=True)
    price = models.FloatField()
    discount_price = models.FloatField(blank=True, null=True)
    category = models.CharField(choices=CATEGORY_CHOICES, max_length=2)
    label = models.CharField(choices=LABEL_CHOICES, max_length=1)
    slug = models.SlugField()
    description = models.TextField()
    image = models.ImageField(upload_to=upload_location, blank=True, null=True)
    stock_quantity = models.IntegerField(default=0)

class OrderItem(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL,
                             on_delete=models.CASCADE)
    ordered = models.BooleanField(default=False)
    item = models.ForeignKey(Item, on_delete=models.CASCADE)
    item_variations = models.ManyToManyField(ItemVariation)
    quantity = models.IntegerField(default=1)
    purchase = models.FloatField(blank=True, null=True)


    def get_total_item_price(self):
        return self.quantity * self.item.price 

class Order(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL,
                             on_delete=models.CASCADE)
    ref_code = models.CharField(
        max_length=20, blank=True, null=True, unique=True)
    items = models.ManyToManyField(OrderItem)
    start_date = models.DateTimeField(auto_now_add=True)
    # Check this
    ordered_date = models.DateTimeField()
    # When the payment is made it becomes True
    ordered = models.BooleanField(default=False)
    shipping_address = models.ForeignKey(
        'Address', related_name='shipping_address', on_delete=models.SET_NULL, blank=True, null=True)
    billing_address = models.ForeignKey(
        'Address', related_name='billing_address', on_delete=models.SET_NULL, blank=True, null=True)
    payment = models.ForeignKey(
        'Payment', on_delete=models.SET_NULL, blank=True, null=True)
    coupon = models.ForeignKey(
        'Coupon', on_delete=models.SET_NULL, blank=True, null=True)
    being_delivered = models.BooleanField(default=False)
    received = models.BooleanField(default=False)
    refund_requested = models.BooleanField(default=False)
    refund_granted = models.BooleanField(default=False)
    refund_refused = models.BooleanField(default=False)

任何帮助将不胜感激，谢谢。

Answer 1

您可以将 ItemPrice 作为具有一对多关系的单独模型。项目的哪些价格已存储，相关日期已更改。

models.py

class ItemPrice(models.Model):
    item = models.ForeignKey(Item, on_delete=models.CASCADE) 
    price = models.FloatField()
    date_changed = models.DateTimeField(auto_now=True, blank=True, null=True)

然后将您的订单日期与当时的商品价格对齐。

更新 Django 中的模型实例，使旧实例及其与其他实例的关系不受影响

Update an instance of a model in django such that the older instance and its relationship with other instances remain unaffected

django

django-models

django-shop