覆盖Django(DRF)序列化程序对象GET [英] Override Django (DRF) Serializer object GET

问题描述

我正在尝试注入"一些 raw sql 到我的DRF嵌套序列化程序中:

 <代码>#SERIALIZERSCarSerializer类(serializers.ModelSerializer):类Meta:型号=汽车字段='__all__'类DriverSerializer(serializers.ModelSerializer):car = CarSerializer()#< ---在这里，我不想获取Car对象，而是注入一个原始sql.类Meta:型号=驱动程序字段='__all__' 

由于我使用的是MariaDB版本表，因此需要SQL注入来请求数据的特定版本，但这无关紧要.如何覆盖从 CarSerializer 获取对象的方法?谢谢.

解决方案

感谢大家的回答，尽管我的解决方案不像@yvesonline和@iklinak所建议的那样干净，但我设法使它起作用:

我首先查看了有关覆盖序列化程序的官方DRF文档: https://www.django-rest-framework.org/api-guide/serializers/#overriding-serialization-and-deserialization-behavior

我特别对方法的重写感兴趣: .to_representation(self，instance)，该方法控制从数据库中获取对象:

从datetime

 导入日期时间为dt从集合中导入OrderedDict从rest_framework.relations导入PKOnlyObject从rest_framework.fields导入SkipField，为空def __init __(self，instance = None，data = empty，asTime = str(dt.now())，** kwargs):self.asTime = asTimeself.instance =实例如果数据不为空:self.initial_data =数据self.partial = kwargs.pop('partial'，False)self._context = kwargs.pop('context'，{})kwargs.pop('很多'，无)super().__ init __(** kwargs)def to_representation(自己，实例):#用我的原始查询替换实例#警告:self.asTime是自定义变量，请检查#上面的__init__方法！实例= Car.objects.raw('''从db_car选择*截至时间戳记％s的system_time其中id =％s;'''，[self.asTime，instance.id])[0]ret = OrderedDict()字段= self._read_fields对于字段中的字段:尝试:属性= field.get_attribute(实例)除了SkipField:继续check_for_none = attribute.pk，如果isinstance(属性，PKOnlyObject)else属性如果check_for_none为None:ret [field.field_name] =无别的:ret [field.field_name] = field.to_representation(属性)返回ret 

您可以在此处找到原始代码: class DriverSerializer(serializers.ModelSerializer):汽车= CarSerializer(asTime ='2021-02-05 14:34:00')类Meta:型号=驱动程序字段='__all__'

I'm trying to "inject" some raw sql into my DRF nested Serializer:

# SERIALIZERS

class CarSerializer(serializers.ModelSerializer):

    class Meta:
        model = Car
        fields = '__all__'

class DriverSerializer(serializers.ModelSerializer):
    car = CarSerializer()   # <--- here I don't want to get the Car object but rather inject a raw sql.

    class Meta:
        model = Driver
        fields = '__all__'

The SQL injection is needed to request for a specific version of the data since I'm using MariaDB versioning tables but this is not relevant. How do I override the method that gets the object from CarSerializer? Thank you.

解决方案

Thank you everyone for your answers, I managed to make it work although my solution is not as clean as the one suggested from @yvesonline and @iklinak:

I first checked the official DRF documentation on overriding serializers: https://www.django-rest-framework.org/api-guide/serializers/#overriding-serialization-and-deserialization-behavior

In particular I was interested in the overriding of the method: .to_representation(self, instance) that controls the fetching of the object from the database:

from datetime import datetime as dt
from collections import OrderedDict
from rest_framework.relations import PKOnlyObject
from rest_framework.fields import SkipField, empty

    def __init__(
            self, instance=None, data=empty, asTime=str(dt.now()), **kwargs):
        self.asTime = asTime
        self.instance = instance
        if data is not empty:
            self.initial_data = data
        self.partial = kwargs.pop('partial', False)
        self._context = kwargs.pop('context', {})
        kwargs.pop('many', None)
        super().__init__(**kwargs)

    def to_representation(self, instance):
        # substitute instance with my raw query
        # WARNING: self.asTime is a custom variable, check the
        # __init__ method above!

        instance = Car.objects.raw(
            '''
                    select * from db_car
                    for system_time as of timestamp %s
                    where id=%s;
                ''', [self.asTime, instance.id])[0]

        ret = OrderedDict()
        fields = self._readable_fields

        for field in fields:
            try:
                attribute = field.get_attribute(instance)
            except SkipField:
                continue

            check_for_none = attribute.pk if isinstance(
                attribute, PKOnlyObject) else attribute
            if check_for_none is None:
                ret[field.field_name] = None
            else:
                ret[field.field_name] = field.to_representation(attribute)

        return ret

You can find the original code here: https://github.com/encode/django-rest-framework/blob/19655edbf782aa1fbdd7f8cd56ff9e0b7786ad3c/rest_framework/serializers.py#L335

Then finally in the DriverSerializer class:

class DriverSerializer(serializers.ModelSerializer):
    car = CarSerializer(asTime='2021-02-05 14:34:00')

    class Meta:
        model = Driver
        fields = '__all__'

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