Django中访问多级课程页面出现404（页面未找到）错误排查

Hey there, let's break down why you're hitting that 404 error when accessing URLs like /courses/1/1/ or /courses/1/2/, and fix it step by step.

问题根源 #

You're trying to access URLs with two levels of parameters (course ID + step ID), but your current code only has a view (course_detail) that handles a single parameter, plus no matching URL route for the multi-level path. Django can't find a matching view, so it throws the 404.

第一步：新增处理步骤详情的视图 #

Update your courses/views.py to add a view that handles both course and step IDs. This view will fetch the specific course first, then the matching step under that course:

from django.shortcuts import get_object_or_404, render
from .models import Course, Step

def course_list(request):
    courses = Course.objects.all()
    return render(request, 'courses/course_list.html', {'courses': courses})

def course_detail(request, pk):
    course = get_object_or_404(Course, pk=pk)
    return render(request, 'courses/course_detail.html', {'course': course})

# 新增：处理课程下具体步骤的视图
def step_detail(request, course_pk, step_pk):
    # 先验证课程存在，再验证该课程下的步骤存在
    course = get_object_or_404(Course, pk=course_pk)
    step = get_object_or_404(Step, pk=step_pk, course=course)
    return render(request, 'courses/step_detail.html', {'course': course, 'step': step})

第二步：配置匹配多级参数的URL路由 #

Next, add a URL rule that matches the two-level path. If you're using an app-specific urls.py (recommended), modify courses/urls.py like this:

from django.urls import path
from . import views

urlpatterns = [
    path('', views.course_list, name='course_list'),
    # 注意：更具体的URL要放在更通用的URL前面！
    path('<int:course_pk>/<int:step_pk>/', views.step_detail, name='step_detail'),
    path('<int:pk>/', views.course_detail, name='course_detail'),
]

Important: Order matters here. The two-parameter path needs to come before the single-parameter one, otherwise Django will match /courses/1/1/ to the course_detail view (using 1 as the course ID) and ignore the step parameter.

第三步：确认模板文件存在 #

Make sure you've created a step_detail.html template in courses/templates/courses/ to render the step content. You can populate it with data from the course and step variables passed from the view.

额外检查点 #

• Verify your Step model has a foreign key linking to Course:

  class Step(models.Model):
      course = models.ForeignKey(Course, on_delete=models.CASCADE)
      # Add other fields (like title, content) here
  

• Double-check that you have existing Course and Step entries in your database—get_object_or_404 will throw a 404 if the requested IDs don't exist.

Once you've made these changes, accessing URLs like http://127.0.0.1:8000/courses/1/1/ should load the correct step detail page without the 404 error.

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