我如何在模板中使用反向关系项django

Question

 {% for order in orders %}
  <li>{{order.customer.last_name}} - {{ order.orderitem_set.product.unit_price }}</li>
  {% endfor %}

class Product(models.Model):
    title = models.CharField(max_length=255)
    slug = models.SlugField()
    description = models.TextField()
    unit_price = models.DecimalField(max_digits=6, 
    decimal_places=2)
    inventory = models.IntegerField()
    last_update = models.DateTimeField(auto_now=True)
    collection = models.ForeignKey(Collection, 
    on_delete=models.PROTECT)
    promotions = models.ManyToManyField(Promotion)

class Order(models.Model):
    placed_at = models.DateTimeField(auto_now_add=True)
    customer = models.ForeignKey(Customer, 
    on_delete=models.PROTECT)

class OrderItem(models.Model):
    order = models.ForeignKey(Order, on_delete=models.PROTECT)
    product = models.ForeignKey(Product, on_delete=models.PROTECT)
    quantity = models.PositiveSmallIntegerField()
    unit_price = models.DecimalField(max_digits=6, 
    decimal_places=2)

我如何在浏览器中获得unit_price，last_name显示，但是当我尝试使用django反向关系创建的项目时，值不显示值

Answer 1

订单可以由多个项目组成，您必须在集合上迭代（反向关系）：

{% for item in order.orderitem_set.all %}
    {{ item.product.title }}
{% endfor %}

habe a the 查询反向关系。