在Django REST Framework中通过URL多参数获取对象的实现问题

我想通过URL中的多个参数（比如customer/3/order/1/或customer/<int:customer_pk>/order/<int:pk>/）获取对象，Shell中可以正常实现：

>>> from temp.models import Customer, Order
>>> from temp.serializers import CustomerSerializer, OrderSerializer
>>> q = Order.objects.filter(customer=1).get(order_number=2)
>>> q.order_name
'fruit'

但在Django REST Framework视图中无法实现，当前代码如下：

views.py #

from rest_framework import generics
from rest_framework.views import APIView

from .models import *
from .serializers import *

class OrderDetailView(generics.RetrieveDestroyAPIView):
    serializer_class = OrderSerializer 

    def get_queryset(self):
        queryset = Order.objects.filter(customer_id=self.kwargs["customer_pk"]).get(order_number=self.kwargs["pk"])
        return queryset

urls.py #

from django.urls import path

from .views import *

urlpatterns = [   
    path('<int:customer_pk>/orders/<int:pk>/', OrderDetailView.as_view()),    
]

你的代码核心问题是：RetrieveDestroyAPIView要求get_queryset方法返回QuerySet类型对象，但你用.get()直接返回了单个Order实例，这会导致视图逻辑出错（视图后续会对查询集进行迭代或过滤操作，单个实例不支持这些方法）。

下面是两种可行的修正方式：

方式1：重写get_object方法（推荐） #

直接在get_object中通过两个参数获取单个对象，这是多参数筛选单个实例的标准做法：

from rest_framework import generics
from .models import Order
from .serializers import OrderSerializer

class OrderDetailView(generics.RetrieveDestroyAPIView):
    serializer_class = OrderSerializer 

    def get_object(self):
        # 根据customer_pk和order_number（对应URL中的pk参数）获取对象
        return Order.objects.get(
            customer_id=self.kwargs["customer_pk"],
            order_number=self.kwargs["pk"]
        )

方式2：修正get_queryset返回QuerySet #

如果希望保留get_queryset的逻辑，需要返回过滤后的QuerySet，由视图自行根据pk（即order_number）获取对象。注意：如果Order模型的主键不是order_number，需要额外指定lookup_field：

from rest_framework import generics
from .models import Order
from .serializers import OrderSerializer

class OrderDetailView(generics.RetrieveDestroyAPIView):
    serializer_class = OrderSerializer
    # 指定用order_number作为查找字段，对应URL中的pk参数
    lookup_field = "order_number"

    def get_queryset(self):
        # 返回指定customer的所有订单QuerySet
        return Order.objects.filter(customer_id=self.kwargs["customer_pk"])

可选：优化URL路径 #

为了让URL语义更清晰，可以给路径加上customer/前缀：

from django.urls import path
from .views import OrderDetailView

urlpatterns = [   
    path('customer/<int:customer_pk>/orders/<int:pk>/', OrderDetailView.as_view()),    
]

内容的提问来源于stack exchange，提问作者mRezaAnanta