类型错误：update() 需要 2 个位置参数，但给出了 3 个：Python

Question

我收到TypeError : update() takes 2 positional arguments but 3 were given 。 我不知道为什么会发生此错误。 如果有人能弄清楚我在哪里做错了，那么将不胜感激。 非常感谢你。

序列化程序.py：

class ShopOwnerOrderManageSerializer(Serializer):
    invoice_no = CharField(read_only=True)
    shopowner_expected_date  = CharField(allow_blank=True)
    shopowner_estimated_time = CharField(allow_blank=True)
    status = CharField(allow_blank=True)

    class Meta:
        model = CarOwnerShopConfirm
        fields= ['shopowner_expected_date','shopowner_estimated_time','status']

    def update(self,validated_data):
        shopowner_expected_date        = validated_data['shopowner_expected_date'] 
        shopowner_estimated_time       = validated_data['shopowner_estimated_time'] 
        status                         = validated_data['status']

        shopconfirm_obj = CarOwnerShopConfirm.objects.update(
                shopowner_expected_date   =   shopowner_expected_date,
                shopowner_estimated_time = shopowner_estimated_time,
                status = status
                )       
        shopconfirm_obj.save()
    
        return validated_data  

Answer 1

Serializer update采用三个参数： self 、 * instance*和验证数据。 通常情况下，数据库不保存在数据库中的变化，但只更新实例。 例如，视图随后可以决定通过调用.save()来更新数据库。

您可能还想使用ModelSerializer ，因为简单的Serializer不考虑Meta内部类，因此不会将序列化器字段“绑定”到对象的这些字段：

class ShopOwnerOrderManageSerializer(ModelSerializer):
    invoice_no = CharField(read_only=True)
    shopowner_expected_date  = CharField(allow_blank=True)
    shopowner_estimated_time = CharField(allow_blank=True)
    status = CharField(allow_blank=True)

    class Meta:
        model = CarOwnerShopConfirm
        fields= ['shopowner_expected_date','shopowner_estimated_time','status']

    def update(self, instance, validated_data):
        instance.shopowner_expected_date = validated_data.get('shopowner_expected_date', instance.shopowner_expected_date)
        instance.shopowner_estimated_time = validated_data.get('shopowner_estimated_time', intance.shopowner_estimated_time)
        instance.status = validated_data.get('status', instance.status)
        return instance

然而，由于 Django 的ModelSerializer会像我们在这里所做的那样实现update ，你可以完全省略它：

class ShopOwnerOrderManageSerializer(ModelSerializer):
    invoice_no = CharField(read_only=True)
    shopowner_expected_date  = CharField(allow_blank=True)
    shopowner_estimated_time = CharField(allow_blank=True)
    status = CharField(allow_blank=True)

    class Meta:
        model = CarOwnerShopConfirm
        fields= ['shopowner_expected_date','shopowner_estimated_time','status']

    #  update