Got it, let's make sure your namespace configuration is spot-on so that the Startup link in your main app's base template works without a hitch. Here's the step-by-step breakdown:

1. Add the Namespace to Your Startup App's URLs #

First, head over to startup/urls.py and set the app_name variable—this is what defines the namespace for all URLs in the startup app. Then make sure your index view has the correct name:

from django.urls import path
from . import views

# This line is critical for the namespace to work
app_name = 'startup'

urlpatterns = [
    # Maps the root of the startup app to your index view, named 'index'
    path('', views.index, name='index'),
]

2. Update Your Project's Main URLs File #

In your project's root urls.py, ensure you're including the startup app's URLs correctly. Since we set app_name in the app's urls.py, Django will automatically recognize the startup namespace when you include it:

from django.conf.urls import include, url
from django.contrib import admin

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^main/', include('main.urls')),
    # Include the startup app's URLs—namespace is pulled from app_name
    url(r'^startup/', include('startup.urls')),
    url(r'^visit/', include('visit.urls')),
]

3. Confirm Your Template Link is Correct #

Your existing link in main/templates/main/base.html is already using the right syntax for namespaced URLs—great job on that! Just double-check for typos (namespace and URL names are case-sensitive):

<li class="nav-item">
    <a class="nav-link" href="{% url 'startup:index' %}">Startup</a>
</li>

Quick Troubleshooting If You Hit Issues #

If you see a NoReverseMatch error, run through these checks:

• Did you add app_name = 'startup' to startup/urls.py? This is the most common missed step.
• Does the index URL pattern in startup/urls.py have name='index' exactly?
• Is your main urls.py including startup.urls without typos?
• Are there any typos in the {% url %} tag (e.g., StartUp instead of startup)?

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