Django error: Reverse for 'detail' with arguments '('',)' not found. 1 pattern(s) tried: ['items/(?P<pk>[0-9]+)/\\Z']

Question

Models.py:

from django.contrib.auth.models import User
from django.db import models

class Category(models.Model):
    name = models.CharField(max_length=225)

    class Meta:
        verbose_name_plural = 'Categories'

    def __str__(self):
        return self.name

class Item(models.Model): 
      Category = models.ForeignKey(Category,related_name='items', on_delete=models.CASCADE )
      name = models.CharField(max_length=225) 
      description = models.TextField(blank=True, null=True)
      image = models.ImageField(upload_to='item_images', blank=True, null=True)
      created_by = models.ForeignKey(User, related_name='items', on_delete=models.CASCADE)
      created_at = models.DateTimeField(auto_now_add=True)


      def __str__(self):
        return self.name

views.py:

from django.shortcuts import render , get_object_or_404

from .models import Item

def detail(request, pk):
    item = get_object_or_404(Item, pk=pk)

    return render(request, 'item/detail.html',{
        'item': item
    })

detail.html:

{% extends 'core/base.html' %}

{% block title %}{{ item.name }}{% endblock %}

{% block content %}

<div class="grid grid-cols-5 gap-6">
    <div class="col-span-3">
        <img src="{{ item.image.url }}" class="rounded-xl">
    </div>
</div>

{% endblock %}

index.html:

{% extends 'core/base.html' %}

{% block title %}Welcome{% endblock %}
{% block content %}
<div class="mt-6 px-6 py-12 bg-gray-100 rounded-xl">
        <h2 class="mb-12 text-2xl text-center">Newest Oportunity</h2>

        <div class="grid grid-cols-3 gap-3">
                {% for item in items %}
                <div>
                        <a href="#">
                                <div>
                                        <img src="{{ item.image.url }}" class="rounded-t-xl">
                                </div>
                                <div class="p-6 bg-white rounded-b-xl">
                                        <h2 class="text-2xl">{{ item.name }}</h2>
                                </div>
                        </a>
                </div>
                {% endfor %}
        </div>
</div>

<div class="mt-6 px-6 py-12 bg-gray-100 rounded-xl">
        <h2 class="mb-12 text-2xl text-center">Categories</h2>
        <div class="grid grid-cols-3 gap-3">
                {% for category in categories %}
                <div>
                        <a href="{% url 'item:detail' item.id %}">

                                
                                <div class="p-6 bg-white rounded-b-xl">
                                        <h2 class="text-2xl">{{ category.name }}</h2>
                                        <p class="text-gray-500">{{ category.items.count }} items</p>
                                </div>
                        </a>
                </div>
                {% endfor %}
        </div>
</div>
{% endblock %}

urls.py:

from django.urls import path
from . import views

app_name = 'item'

urlpatterns = [
    path('<int:pk>/', views.detail, name='detail'),
] 

urls.py:

from django.conf import settings
from django.conf.urls.static import static
from django.contrib import admin
from django.urls import path, include

from core.views import index, contact

urlpatterns = [
    path('contact/',contact, name='contact'),
    path('items/', include('item.urls')),
    path('', index, name='index'),
    path("admin/", admin.site.urls),
] + static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)

error:

Reverse for 'detail' with arguments '('',)' not found. 1 pattern(s) tried: ['items/(?P<pk>[0-9]+)/\\Z']

I was expecting that when I click on the item it will give me specific details on a different page because each category has different items. The problem seems to be in the way I am passing the primary key. I am using Anaconda 3 and Visual Studio Code.

Answer 1

you have item.id inside the category for loop. I suppose you want to have it before in the items for loop. Inside the category for loop it is empty:

                {% for category in categories %}
                <div>
                        <a href="{% url 'item:detail' item.id %}">

                                
                                <div class="p-6 bg-white rounded-b-xl">
                                        <h2 class="text-2xl">{{ category.name }}</h2>
                                        <p class="text-gray-500">{{ category.items.count }} items</p>
                                </div>
                        </a>
                </div>
                {% endfor %}