Reverse for 'post_detail' with arguments '('chempion',)' not found. 1 pattern(s) tried: ['(?P<category_slug>

Question

Reverse for 'post_detail' with arguments '('chempion',)' not found. 1 pattern(s) tried: ['(?P<category_slug>[-a-zA-Z0-9_]+)/(?P[-a-zA-Z0-9_]+)/$']

as soon as I add function and view to templates I catch this error

view.py

def post_detail(request, category_slug, slug):
    post = get_object_or_404(Post, slug=slug)

    try:
        next_post = post.get_next_by_date_added()
    except Post.DoesNotExist:
        next_post = None

    try:
        previous_post = post.get_previous_by_date_added()
    except Post.DoesNotExist:
        previous_post = None

    context = {
        'post': post,
        'next_post': next_post,
        'previous_post': previous_post
    }

    return render(request, 'post_detail.html', context)

urls.py

  path('<slug:category_slug>/<slug:slug>/', post_detail, name='post_detail'),
    path('<slug:slug>/', category_detail, name='category_detail'),

post detail.html

 {% if next_post %}
    <a href="{% url 'post_detail' next_post.slug %}">Next</a>
 {% else %}
    This is the last post!
 {% endif %}

Answer 1

The post_detail view requires two slugs: one of slug for the category, and one for the post.

If your Post model for example has a ForeignKey to the Category model, you can reference this with:

<a href="{% url 'post_detail' next_post.category.slug next_post.slug %}">Next</a>

In your view, you might want to check both the slug for the category and for the post, so:

def post_detail(request, category_slug, slug):
    post = get_object_or_404(Post, category__slug=category_slug, slug=slug)
    # …