使用参数 '('',)' 和关键字参数 '{}' 未找到的 'post_detail' 反转。 尝试了 1 个模式：['posts/(?P[0-9]+)/$']

Question

I have this error :

Reverse for 'post_detail' with arguments '('',)' and keyword arguments '{}' not found. 1 pattern(s) tried: ['posts/(?P[0-9]+)/$']

from the line 7 in home.html template :

<a href="{% url 'post_detail' post.id %}">{{ post.title }}</a>

From home.html

<h1>Welcome to Jeremie's blog</h1>

<h2>Latest Posts</h2>

{% for posts in posts.all %}

<a href="{% url 'post_detail' post.id %}">{{ post.title }}</a>
<br />
{{ posts.pub_date_pretty }}
<br />
<img src = "{{ post.image.url }}" />
<br />
{{ posts.summary }}
<br />
<br />

{% endfor %}

From posts_details.html

{{ post.title }}
<br />
{{ posts.pub_date_pretty}}
<br />
<img src = "{{ post.image.url }}" />
<br />
{{posts.summary}}
<br />
<br />

From urls.py

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^$', views.home),
    url(r'^posts/(?P<post_id>[0-9]+)/$', views.post_details, name="post_detail"),

] + static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)

From views.py

def home(request):
    posts = Post.objects.order_by('pub_date')
    return render(request, 'posts/home.html', {'posts':posts})

def post_details(request, post_id):
    post = get_object_or_404(Post, pk=post_id)
    return render(request, 'posts/posts_detail.html', {'post':post})

From models.py

class Post(models.Model):
    title = models.CharField(max_length=255)
    pub_date = models.DateTimeField()
    image = models.ImageField(upload_to='media')
    body = models.TextField()

    def __str__(self):
        return self.title

    def pub_date_pretty(self):
        return self.pub_date.strftime('%b %e %Y')

    def summary(self):
        return self.body[:100]

It seems that post.id isn't available in the template. However, it is well defined in views.py .

Could anyone be able to tell me how could I fix this problem?

Answer 1

It seems that you don't have post.id available in the template, probably because the post isn't created yet. If I don't know your logic patterns, I can't tell you exactly why the post.id isn't there, but you see that post.id is an empty string from the error message: Reverse for 'post_detail' with arguments '('',)' and keyword arguments '{}' not found. 1 pattern(s) tried: ['posts/(?P[0-9]+)/$'] Reverse for 'post_detail' with arguments '('',)' and keyword arguments '{}' not found. 1 pattern(s) tried: ['posts/(?P[0-9]+)/$'] where the arguments is a tuple of one item that is an empty string, namely this: ('', ) . In the quotations there should be the ID, a number.

Answer 2

You're not being consistent in your home.html template on whether the variable is post or posts . Pick one - post makes more sense - and stick to it.

{% for post in posts.all %}

<a href="{% url 'post_detail' post.id %}">{{ post.title }}</a>
{{ post.pub_date_pretty }}
<img src = "{{ post.image.url }}" />
{{ post.summary }}

{% endfor %}

(Also, not related but note that it's extremely poor practice to use br tags like that. Please use proper semantic markup and use CSS to manage the space between elements.)