使用drf-nested-routers遇URL解析错误，无法获取Section详情

Hey there! Let's break down what's going wrong here and fix it step by step.

Key Issues Identified #

1. Mismatched Lookup Fields
   Your Course and Section models use custom primary keys (course_code and section_number respectively), but the default viewset behavior expects the standard pk field. This causes URL resolution failures when fetching details.

2. Incorrect View Names for Nested Routes
   The drf-nested-routers generates view names in the format <parent-lookup>-<route>-detail (e.g., parent_course-sections-detail), but your serializers were referencing the generic section-detail which doesn't exist in the nested setup.

3. Unfiltered Section Queries
   Your SectionViewSet wasn't filtering results by the parent course from the URL, so it tried to return all sections regardless of the course context.

Fixed Code Implementation #

/views.py

from . import models
from . import serializers
from rest_framework import viewsets

class CourseViewSet(viewsets.ModelViewSet):
    serializer_class = serializers.CourseSerializer
    queryset = models.Course.objects.all()
    # Match the custom primary key of Course model
    lookup_field = 'course_code'

class SectionViewSet(viewsets.ModelViewSet):
    serializer_class = serializers.SectionSerializer
    queryset = models.Section.objects.all()
    # Match the custom primary key of Section model
    lookup_field = 'section_number'

    def get_queryset(self):
        # Filter sections to only those linked to the parent course in the URL
        parent_course_code = self.kwargs.get('parent_course_pk')
        if parent_course_code:
            return self.queryset.filter(parent_course__course_code=parent_course_code)
        return super().get_queryset()

/serializers.py

from rest_framework_nested.relations import NestedHyperlinkedRelatedField
from rest_framework_nested.serializers import NestedHyperlinkedModelSerializer
from rest_framework import serializers
from . import models

class CourseSerializer(serializers.HyperlinkedModelSerializer):
    sections_offered = NestedHyperlinkedRelatedField(
        many=True,
        read_only=True,
        # Use the correct nested view name generated by the router
        view_name='parent_course-sections-detail',
        parent_lookup_kwargs={'parent_course_pk': 'parent_course__course_code'}
    )

    class Meta:
        model = models.Course
        fields = ("url", "course_code", "sections_offered",)
        # Ensure the course URL uses the custom primary key
        extra_kwargs = {'url': {'lookup_field': 'course_code'}}

class SectionSerializer(NestedHyperlinkedModelSerializer):
    class Meta:
        model = models.Section
        fields = "__all__"
        # Map the nested route parameters to model fields
        parent_lookup_kwargs = {'parent_course_pk': 'parent_course__course_code'}
        # Ensure the section URL uses its custom primary key
        extra_kwargs = {'url': {'lookup_field': 'section_number'}}

/urls.py (no changes needed, just confirmation)

Your existing setup is correct— the NestedSimpleRouter generates the right view names that we now reference in the serializers:

from rest_framework import routers
from . import views
from rest_framework_nested.routers import NestedSimpleRouter
from django.conf.urls import url, include

router = routers.DefaultRouter()
router.register(r'courses', views.CourseViewSet)
courses_router = NestedSimpleRouter(router, r'courses', lookup='parent_course')
courses_router.register(r'sections', views.SectionViewSet)

urlpatterns = [
    url(r'^', include(router.urls)),
    url(r'^', include(courses_router.urls)),
]

What These Changes Fix #

• /courses/CS250/sections/ will now only list sections belonging to CS250 (even after creating sections)
• The section detail URL (/courses/CS250/sections/01/) resolves correctly without errors
• The sections_offered links in course detail responses point to valid nested section URLs
• Both models use their custom primary keys for URL lookup, matching your database structure

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