显示外键值

Question

我的 models.py 看起来像这样：class Order(models.Model):    items = models.ManyToManyField(OrderItem)class OrderItem(models.Model): (item in the cart)   item = models.ForeignKey(Item, on_delete=models.CASCADE)class Item(models.Model):    title = models.CharField(max_length=100)    price = models.FloatField()    discount_price = models.FloatField(blank=True, null=True)    label = models.ManyToManyField(Label, blank=True)    slug = models.SlugField(unique=True)    description = models.TextField()class Bike(models.Model):    item = models.OneToOneField(Item, on_delete=models.CASCADE)    brand = models.ManyToManyField(Brand)    size = models.ManyToManyField(Size, blank=True)class Accessory(models.Model):    item = models.OneToOneField(Item, on_delete=models.CASCADE)    brand_accessory = models.ManyToManyField(BrandAccessory)所以目前item我OrderItem模型中的字段显示模型中项目的标题和数量Item：def __str__(self):    return f"{self.quantity} of {self.item.title}"ItemOneToOneField与Bike和连接Accessory。是否可以显示品牌和尺寸，Bike如果它被添加到OrderItem，brand_accessory如果Accessory被添加到OrderItem？它看起来像 {quantity} {item.title}（如果是自行车）> {bike.brand} {bike.size}（如果附件）> {accessory.brand_accessory}

Answer 1

您可以使用hasattr检查您item是否需要 OneToOneField

class OrderItem(models.Model):

    ...

    def __str__(self):

        if hasattr(self.item, 'bike'):

            #get value you need like: self.item.bike.brand

        if hasattr(self.item, 'accessory'):

            #get value you need like: self.item.accessory.brand_accessory

        return #get values you need together