使用Extra字段序列化多对多关系

Question

请我试图解决这个问题。猜猜看到其他类似的问题之后我还没有得到什么。

我有这些模型：

class Dish(BaseModel):
    class Meta:
        verbose_name_plural = 'dishes'
    name = models.CharField(_('dish'), max_length=100)
    dish_type = models.CharField(_("dish type"), max_length=100)
    price = models.PositiveIntegerField(_("price"))

    def __str__(self):
        return f"{self.name} costs {self.price}"


class Order(BaseModel):

    dishes = models.ManyToManyField(Dish, through='DishOrder')
    customer = models.ForeignKey(Customer, on_delete=models.CASCADE)
    discount = models.PositiveIntegerField(_("total discount"), blank=True)
    total = models.PositiveIntegerField(_("total"), blank=True)
    shipping = models.PositiveIntegerField(_("shipping cost"), blank=True)
    grand_total = models.PositiveIntegerField(_("grand total"), blank=True)
    country = models.CharField(_('country code'), max_length=2)

    def __str__(self):
        return f"order from {self.customer} at {self.total}"

    def get_absolute_url(self):
        return reverse('order-details', kwargs={'pk': self.pk})


class DishOrder(models.Model):
    dish = models.ForeignKey(Dish, on_delete=models.CASCADE, related_name='dishes')
    order = models.ForeignKey(Order, on_delete=models.CASCADE, related_name='dishes')
    quantity = models.PositiveIntegerField(_("quantity"))
    discount = models.PositiveIntegerField(_("discount"))
    price = models.PositiveIntegerField(_('price'))

和相应的序列化器如下：

class DishOrderSerializer(serializers.ModelSerializer):
    class Meta:
        model = DishOrder
        fields = (
            "quantity",
            "discount",
            "price"
        )

class OrderSerializer(serializers.ModelSerializer):
    dishes = DishOrderSerializer(source='dish', many=True)
    class Meta:
        model = Order
        fields = (
            "id",
            "country",
            "customer",
            "dishes", 
            "total", 
            "discount",
            "grand_total",
            "voucher"
        )

可以看出，我通过直通表有一个m2m的关系。但是我无法让序列化器工作。这是我不断得到的错误：

尝试在序列化程序dishes上获取字段OrderSerializer的值时获得AttributeError。序列化程序字段可能名称不正确，并且与Order实例上的任何属性或键都不匹配。原始异常文本是：'Order'对象没有属性'dish'。

我一直在仔细研究这个问题，试图找出错误是什么。我将不胜感激任何帮助

Answer 1

由于你在模型中使用related_name='dishes'，你应该使用dishes作为manytomany对象的源：

class OrderSerializer(serializers.ModelSerializer):
    dishes = DishOrderSerializer(source='dishes', many=True)

或简单：

class OrderSerializer(serializers.ModelSerializer):
    dishes = DishOrderSerializer(many=True)

由于source='dishes'冗余，以防你将序列化器的字段命名为dishes。