Django链接跳转404错误：期望导向views.PostList.as_view()失败

我设置了导航栏链接指向{% url 'questions' %}，对应路径是http://localhost:8000/questions/，期望它路由到views.PostList.as_view()，但访问时出现404错误：

Page not found (404)
No Post matches the given query.
Request Method: GET
Request URL: http://localhost:8000/questions/
Raised by: blog.views.PostDetail
Using the URLconf defined in classroommatrix.urls, Django tried these URL patterns, in this order:

admin/
index/ [name='index']
slug:slug/ [name='post_detail']
The current path, questions/, matched the last one.

超链接代码位于templates/base.html第46行：

<a class="nav-link" href="{% url 'questions' %}">Top Questions</a>

已做的调试检查 #

1. 检查blog/urls.py的URL模式 #

当前的URL配置如下：

# blog/urls.py (通过classroommatrix/urls.py调用)

from . import views
from django.urls import path


urlpatterns = [ # 博客应用的URL模式
    path('index/', views.PostList.as_view(), name='index'), # 首页
    path('<slug:slug>/', views.PostDetail.as_view(), name='post_detail'), # 文章详情页
    path('like/<slug:slug>', views.PostLike.as_view(), name='post_like'), # 文章点赞
    path('questions/', views.PostList.as_view(), name='questions'), # 问题页面
]

2. 检查PostDetail视图类 #

该类仅处理文章详情逻辑，未涉及questions路径：

# blog/views.py

from django.shortcuts import render, get_object_or_404, reverse
from django.views import generic, View
from django.http import HttpResponseRedirect
from .models import Post
from .forms import CommentForm


class PostList(generic.ListView): # 展示所有文章的列表视图
    model = Post
    queryset = Post.objects.filter(status=1).order_by("-created_on")
    template_name = "questions.html"
    paginate_by = 6


class PostDetail(View): # 文章详情视图
    def get(self, request, slug, *args, **kwargs):
        queryset = Post.objects.filter(status=1)
        post = get_object_or_404(queryset, slug=slug)
        comments = post.comments.filter(approved=True).order_by("-created_on")
        liked = False
        if post.likes.filter(id=self.request.user.id).exists():
            liked = True

        return render(
            request,
            "post_detail.html",
            {
                "post": post,
                "comments": comments,
                "commented": False,
                "liked": liked,
                "comment_form": CommentForm()
            },
        )
    
    def post(self, request, slug, *args, **kwargs):
        queryset = Post.objects.filter(status=1)
        post = get_object_or_404(queryset, slug=slug)
        comments = post.comments.filter(approved=True).order_by("-created_on")
        liked = False
        if post.likes.filter(id=self.request.user.id).exists():
            liked = True

        comment_form = CommentForm(data=request.POST)
        if comment_form.is_valid():
            comment_form.instance.email = request.user.email
            comment_form.instance.name = request.user.username
            comment = comment_form.save(commit=False)
            comment.post = post
            comment.save()
        else:
            comment_form = CommentForm()

        return render(
            request,
            "post_detail.html",
            {
                "post": post,
                "comments": comments,
                "commented": True,
                "comment_form": comment_form,
                "liked": liked
            },
        )

原因 #

Django的URL匹配是从上到下按顺序匹配的。你当前的urlpatterns中，动态路径<slug:slug>/排在questions/前面，导致访问/questions/时，Django会把questions当作slug参数传给PostDetail视图，试图查找slug为questions的Post，找不到就抛出404错误。

解决方法 #

调整URL模式的顺序，把固定路径questions/移到动态路径<slug:slug>/的前面：

urlpatterns = [ # 博客应用的URL模式
    path('index/', views.PostList.as_view(), name='index'), # 首页
    path('questions/', views.PostList.as_view(), name='questions'), # 问题页面 - 移到动态路径前
    path('<slug:slug>/', views.PostDetail.as_view(), name='post_detail'), # 文章详情页
    path('like/<slug:slug>', views.PostLike.as_view(), name='post_like'), # 文章点赞
]

这样Django会优先匹配固定的questions/路径，正确路由到PostList视图，不会再被动态slug路径拦截。

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