How to create a fullstack application using Django and Python Part 19

Friday, September 20, 2024 at 9:56 AM | 17 min read

Last modified on Thursday, July 16, 2026 at 12:11 PM

#fullstack development, #macOS, #django, #annotate, #login redirect, #protecting views, #python3, #queryset, #series, #tests, #unittest

_Photo by Chittima Stanmore on unsplash.com_

Important Note: Before committing anything to Git or pushing anything to remote, please visit How to create a fullstack application using Django and Python Part 4 where I discuss how to add the python-dotenv package to the Django site and why it is crucial to do it. This article assumes you have a working knowledge of Git.

• How to protect views
• Configuring the login next redirect
  • templates/login.html
• @login_required tests
  • boards/tests/test_login_required_new_topic_tests.py
• Accessing the authenticated user
• The topic posts view
  • Creating the templates/topic_posts.html
  • boards/tests/test_topic_posts_tests.py
  • Creating a for loop to iterate over topic posts in topic_posts.html
  • Updating the topics.html template with URL to the topic posts listing
• The reply post view
  • Adding the post reply URL to django_boards/urls.py
  • Creating a form for the post reply in boards/forms.py
• Update the return redirect of the new_topic view function
• First version of templates/reply_topic.html (without likes or links)
• Making the starter post more prominent on the page
• boards/tests/test_reply_topic_test_case.py
• boards/tests/test_login_required_reply_topic_tests.py
• boards/tests/test_reply_topic_tests.py
• boards/tests/test_successful_reply_topic_tests.py
• boards/tests/test_invalid_reply_topic_tests.py
• QuerySets
  • Improving the index/home view
• Experimenting with the Python shell
• boards/models.py
• Adding the posts count, topics count, and latest post to the index/home view
• Running the tests to include the new ReplyTopic related tests
• Improving the topics view
• Updating the board_topics in boards/views.py
• Updating templates/topics.html
• Adding a new field to the Topic model
• Running makemigrations and migrate
• app.css
• Code associated with this post
• Conclusion
• Related Resources
• Related Posts

Update (July 2026): This walkthrough was written against Django 5.1, which reached full end-of-life in December 2025 and is no longer receiving security patches. Run python -m django --version to check which version you have.

I wrote this series as a live process, so sometimes it might seem confusing, but it all works out in the end.

I have to start protecting my views from non-authorized users. For example, I have the new_topic view for starting a new topic post:

The unprotected new_topic view

Django has a built-in decorator to prevent unauthorized users from being able to access views only meant for logged in users:

# boards/views.py
from django.shortcuts import render, redirect, get_object_or_404
from django.contrib.auth.models import User
from django.contrib.auth.decorators import login_required
from .forms import NewTopicForm
from .models import Board, Topic, Post


# Create your views here.
def index(request):
    boards = Board.objects.all()
    return render(request, "index.html", {"boards": boards})


def board_topics(request, id):
    board = get_object_or_404(Board, id=id)
    return render(request, "topics.html", {"board": board})

@login_required
def new_topic(request, id):
    board = get_object_or_404(Board, id=id)
    user = User.objects.first()  # TODO: get the currently logged in user
    if request.method == 'POST':
        form = NewTopicForm(request.POST)
        if form.is_valid():
            topic = form.save(commit=False)
            topic.board = board
            topic.starter = user
            topic.save()
            post = Post.objects.create(
                message=form.cleaned_data.get('message'),
                topic=topic,
                created_by=user
            )
            return redirect('board_topics', id=board.id)  # TODO: redirect to the created topic page
    else:
        form = NewTopicForm()
    return render(request, 'new_topic.html', {'board': board, 'form': form})

From now on, if the user is not authenticated, they will be redirected to the login page.

Unauthorized user redirect to login page

Notice the http://127.0.0.1:8000/login/?next=/boards/1/new/ URL in the browser? I am going to improve upon the user experience by taking advantage of the Django next redirect variable and improving upon the login template as well.

<!-- templates/login.html -->
{% extends "base_accounts.html" %}

{% load static %}

{% block stylesheet %}
  <link rel="stylesheet" href="{% static 'css/accounts.css' %}">
{% endblock stylesheet %}

{% block body %}
  <div class="container">
    <h1 class="text-center logo my-4">
      <a href="{% url 'index' %}">Django Boards</a>
    </h1>
    <div class="row justify-content-center">
      <div class="col-lg-4 col-md-6 col-sm-8">
        <div class="card">
          <div class="card-body">
            <h3 class="card-title">Log in</h3>
            <form method="post" novalidate>
              {% csrf_token %}
              <input type="hidden" name="next" value="{{ next }}">
              {% include "includes/form.html" %}
              <button type="submit" class="btn btn-primary btn-block">Log in</button>
            </form>
          </div>
          <div class="card-footer text-muted text-center">
            New to Django Boards? <a href="{% url 'signup' %}">Sign up</a>
          </div>
        </div>
        <div class="text-center py-2">
          <small>
            <a href="#" class="text-muted">Forgot your password?</a>
          </small>
        </div>
      </div>
    </div>
  </div>
{% endblock body %}

if I try to login now after being redirected to the login page, I will be taken back (in this case) to the protected new_topic view:

Taken back to the new_topic view after logging in

# boards/tests/test_login_required_new_topic_tests.py
from django.test import TestCase
from django.urls import reverse
from ..models import Board

class LoginRequiredNewTopicTests(TestCase):
    def setUp(self):
        Board.objects.create(name='Django', description='Django board.')
        self.url = reverse('new_topic', kwargs={'id': 1})
        self.response = self.client.get(self.url)

    def test_redirection(self):
        login_url = reverse('login')
        self.assertRedirects(self.response, '{login_url}?next={url}'.format(login_url=login_url, url=self.url))

In the test(s) above, I am trying to make a request to the new_topic view without being authenticated. The expected result is for the request to be redirected to the login view.

# boards/views.py
from django.shortcuts import render, redirect, get_object_or_404
from django.contrib.auth.models import User
from django.contrib.auth.decorators import login_required
from .forms import NewTopicForm
from .models import Board, Topic, Post


# Create your views here.
def index(request):
    boards = Board.objects.all()
    return render(request, "index.html", {"boards": boards})


def board_topics(request, id):
    board = get_object_or_404(Board, id=id)
    return render(request, "topics.html", {"board": board})

@login_required
def new_topic(request, id):
    board = get_object_or_404(Board, id=id)
    if request.method == 'POST':
        form = NewTopicForm(request.POST)
        if form.is_valid():
            topic = form.save(commit=False)
            topic.board = board
            topic.starter = request.user  # <- here
            topic.save()
            Post.objects.create(
                message=form.cleaned_data.get('message'),
                topic=topic,
                created_by=request.user  # <- and here
            )
            return redirect('board_topics', id=board.id)  # TODO: redirect to the created topic page
    else:
        form = NewTopicForm()
    return render(request, 'new_topic.html', {'board': board, 'form': form})

I can test this by creating a new topic:

Creating a new topic using refactored new_topic view

Let’s implement the posts listing page, according to the wireframe below:

Boards app wireframe new topic posts and replies

1. First, I need a route:

# django_boards/urls.py
path('boards/<id>/topics/<topic_id>/', views.topic_posts, name='topic_posts'),

I am now dealing with two keyword args. id is used to identify the Board, and topic_id is used to identify which topic to get from the database.

The matching view inside boards/views.py is the following:

# boards/views.py
def topic_posts(request, id, topic_id):
    topic = get_object_or_404(Topic, board__id=id, id=topic_id)
    return render(request, 'topic_posts.html', {'topic': topic})

I am indirectly getting the current board. The topic model is related to the board model, so I can access the current board.

<!-- templates/topic_posts.html -->
{% extends "base.html" %}
{% block title %}
  {{ topic.subject }}
{% endblock title %}
{% block breadcrumb %}
  <li class="breadcrumb-item">
    <a href="{% url 'index' %}">Boards</a>
  </li>
  <li class="breadcrumb-item">
    <a href="{% url 'board_topics' topic.board.id %}">{{ topic.board.name }}</a>
  </li>
  <li class="breadcrumb-item active">{{ topic.subject }}</li>
{% endblock breadcrumb %}
{% block content %}
{% endblock content %}

Now I am using topic.board.name instead of board.name.

Empty topic_posts view

# boards/tests/test_topic_posts_tests.py
from django.contrib.auth.models import User
from django.test import TestCase
from django.urls import resolve, reverse

from ..models import Board, Post, Topic
from ..views import topic_posts

class TopicPostsTests(TestCase):
    def setUp(self):
        board = Board.objects.create(name='Django', description='Django board.')
        user = User.objects.create_user(username='john', email='john@doe.com', password='123')
        topic = Topic.objects.create(subject='Hello, world', board=board, starter=user)
        Post.objects.create(message='Lorem ipsum dolor sit amet', topic=topic, created_by=user)
        url = reverse('topic_posts', kwargs={'id': board.id, 'topic_id': topic.id})
        self.response = self.client.get(url)

    def test_status_code(self):
        self.assertEqual(self.response.status_code, 200)

    def test_view_function(self):
        view = resolve('/boards/1/topics/1/')
        self.assertEqual(view.func, topic_posts)

<!-- templates/topic_posts.html -->
{% extends "base.html" %}
{% load static %}
{% block title %}
  {{ topic.subject }}
{% endblock title %}
{% block breadcrumb %}
  <li class="breadcrumb-item">
    <a href="{% url 'index' %}">Boards</a>
  </li>
  <li class="breadcrumb-item">
    <a href="{% url 'board_topics' topic.board.id %}">{{ topic.board.name }}</a>
  </li>
  <li class="breadcrumb-item active">{{ topic.subject }}</li>
{% endblock breadcrumb %}
{% block content %}
  <div class="mb-4">
    <a href="#" class="btn btn-primary" role="button">Reply</a>
  </div>
  {% for post in topic.posts.all %}
    <div class="card mb-2">
      <div class="card-body p-3">
        <div class="row">
          <div class="col-2">
            <img src="{% static 'img/avatar.svg' %}"
                 alt="{{ post.created_by.username }}"
                 height="100"
                 width="100"
                 class="w-100">
            <small>Posts: {{ post.created_by.posts.count }}</small>
          </div>
          <div class="col-10">
            <div class="row mb-3">
              <div class="col-6">
                <strong class="text-muted">{{ post.created_by.username }}</strong>
              </div>
              <div class="col-6 text-right">
                <small class="text-muted">{{ post.created_at }}</small>
              </div>
            </div>
            {{ post.message }}
            {% if post.created_by == user %}
              <div class="mt-3">
                <a href="#" class="btn btn-primary btn-sm" role="button">Edit</a>
              </div>
            {% endif %}
          </div>
        </div>
      </div>
    </div>
  {% endfor %}
{% endblock content %}

This is how the topic_posts.html looks like in the browser:

topic_posts view with a user response

Since I don't have a way of uploading images yet, I manually added an image to the static/img/ directory. I created it using draw.io and saved it as an svg.

The code {{ post.created_by.posts.count }} is executing a select count in the database (Posts: 9).

I am also testing if the current post belongs to the authenticated user: {% if post.created_by == user %}, and only the author of the post is able to see the edit button.

This is also where I would add the post likes and links: alongside the reply button. I will get back to this later.

<!-- templates/topics.html -->
{% extends "base.html" %}
{% block title %}
  {{ board.name }} - {{ block.super }}
{% endblock title %}
{% block breadcrumb %}
  <li class="breadcrumb-item">
    <a href="{% url 'index' %}">Boards</a>
  </li>
  <li class="breadcrumb-item active">{{ board.name }}</li>
{% endblock breadcrumb %}
{% block content %}
  <div class="mb-4">
    <a href="{% url 'new_topic' board.id %}" class="btn btn-primary">New topic</a>
  </div>
  <table class="table">
    <thead class="thead-inverse">
      <tr>
        <th>Topic</th>
        <th>Starter</th>
        <th>Replies</th>
        <th>Views</th>
        <th>Last Update</th>
      </tr>
    </thead>
    <tbody>
      {% for topic in board.topics.all %}
        <tr>
          <td>
            <a href="{% url 'topic_posts' board.id topic.id %}">{{ topic.subject }}</a>
          </td>
          <td>{{ topic.starter.username }}</td>
          <td>0</td>
          <td>0</td>
          <td>{{ topic.last_updated }}</td>
        </tr>
      {% endfor %}
    </tbody>
  </table>
{% endblock content %}

The reply post view

# django_boards/urls.py
# place this url right above the admin/ route
path('boards/<id>/topics/<topic_id>/reply/', views.reply_topic, name='reply_topic')

# boards/forms.py
from django import forms
from .models import Topic
from .models import Post # added

class NewTopicForm(forms.ModelForm):
    message = forms.CharField(
        widget=forms.Textarea(
            attrs={"rows": 5, "placeholder": "What is on your mind?"}
        ),
        max_length=4000,
        help_text="The max length of the text is 4000.",
    )

    class Meta:
        model = Topic
        fields = ["subject", "message"]

class PostForm(forms.ModelForm): # added
    class Meta:
        model = Post
        fields = ['message', ]

And now I protect the reply_topic view in boards/views.py:

# boards/views.py
@login_required
def reply_topic(request, id, topic_id):
    topic = get_object_or_404(Topic, board__id=id, id=topic_id)
    if request.method == 'POST':
        form = PostForm(request.POST)
        if form.is_valid():
            post = form.save(commit=False)
            post.topic = topic
            post.created_by = request.user
            post.save()
            return redirect('topic_posts', id=id, topic_id=topic_id)
    else:
        form = PostForm()
    return render(request, 'reply_topic.html', {'topic': topic, 'form': form})

Next, I have to update the return redirect of the new_topic view function (marked with the comment # TODO):

@login_required
def new_topic(request, id):
    board = get_object_or_404(Board, id=id)
    if request.method == 'POST':
        form = NewTopicForm(request.POST)
        if form.is_valid():
            topic = form.save(commit=False)
            topic.board = board
            topic.starter = request.user  # <- here
            topic.save()
            Post.objects.create(
                message=form.cleaned_data.get('message'),
                topic=topic,
                created_by=request.user,  # <- and here
                post_liked_by = request.user # added
            )
            return redirect('topic_posts', id=id, topic_id=topic.id)  # redirect to the created topic (topic_posts) page
    else:
        form = NewTopicForm()
    return render(request, 'new_topic.html', {'board': board, 'form': form})

It's important to note that in the reply_topic view, I am using topic_id, because I am referring to the keyword argument of the function. In the new_topic view, I am using topic.id, because topic is an object (a Topic model instance), and with .id I am accessing the id property of the Topic model instance.

<!-- templates/reply_topic.html -->
{% extends "base.html" %}
{% load static %}
{% block title %}
  Post a reply
{% endblock title %}
{% block breadcrumb %}
  <li class="breadcrumb-item">
    <a href="{% url 'index' %}">Boards</a>
  </li>
  <li class="breadcrumb-item">
    <a href="{% url 'board_topics' topic.board.id %}">{{ topic.board.name }}</a>
  </li>
  <li class="breadcrumb-item">
    <a href="{% url 'topic_posts' topic.board.id topic.id %}">{{ topic.subject }}</a>
  </li>
  <li class="breadcrumb-item active">Post a reply</li>
{% endblock breadcrumb %}
{% block content %}
  <form method="post" class="mb-4">
    {% csrf_token %}
    {% include "includes/form.html" %}
    <button type="submit" class="btn btn-success">Post a reply</button>
  </form>
  {% for post in topic.posts.all %}
    <div class="card mb-2">
      <div class="card-body p-3">
        <div class="row mb-3">
          <div class="col-6">
            <strong class="text-muted">{{ post.created_by.username }}</strong>
          </div>
          <div class="col-6 text-right">
            <small class="text-muted">{{ post.created_at }}</small>
          </div>
        </div>
        {{ post.message }}
      </div>
    </div>
  {% endfor %}
{% endblock content %}

Which looks like the following in the browser:

Topic reply view first version

After posting a reply, the user is redirected to the topic_posts view (topic_posts.html).

<!-- templates/topic_posts.html -->
{% extends "base.html" %}
{% load static %}
{% block title %}
  {{ topic.subject }}
{% endblock title %}
{% block breadcrumb %}
  <li class="breadcrumb-item">
    <a href="{% url 'index' %}">Boards</a>
  </li>
  <li class="breadcrumb-item">
    <a href="{% url 'board_topics' topic.board.pk %}">{{ topic.board.name }}</a>
  </li>
  <li class="breadcrumb-item active">{{ topic.subject }}</li>
{% endblock breadcrumb %}
{% block content %}
  <div class="mb-4">
    <a href="#" class="btn btn-primary" role="button">Reply</a>
  </div>
  {% for post in topic.posts.all %}
  <!-- Change starts here -->
    <div class="card mb-3 {% if forloop.first %}border-light{% endif %}">
      {% if forloop.first %}
        <div class="card-header bg-info text-white align-items-center py-2 px-3">
          <h5>{{ topic.subject }}</h5>
        </div>
      {% endif %}
      <!-- Change ends here -->
      <div class="row no-gutters">
        <div class="col-md-8">
          <div class="card-body col-md-8">
            <div class="col">
              <h5 class="card-title text-muted">{{ post.created_by.username }}</h5>
              <p class="card-text">
                <small class="text-muted">{{ post.created_at }}</small>
              </p>
            </div>
            <p class="mt-4">
              <small>Posts: {{ post.created_by.posts.count }}</small>
            </p>
            <div class="post-message">{{ post.message }}</div>
            {% if post.created_by == user %}
              <div class="mt-3">
                <a href="#" class="btn btn-primary btn-sm" role="button">Edit</a>
              </div>
            {% endif %}
            <div class="mb-3 like-count">Post Likes: {{ post.post_liked_by.count }}</div>
          </div>
        </div>
      </div>
    </div>
  {% endfor %}
{% endblock content %}

Which looks like the following in the browser:

topic_posts view design revamp

I will share my CSS code at the end of this section!

# test_reply_topic_test_case.py
from django.contrib.auth.models import User
from django.test import TestCase
from django.urls import reverse
from ..models import Board, Post, Topic
from ..views import reply_topic

# this is just a setup. "No tests run" when this is run alone.
class ReplyTopicTestCase(TestCase):
    """
    Base test case to be used in all `reply_topic` view tests
    """
    def setUp(self):
        self.board = Board.objects.create(name='Django', description='Django board.')
        self.username = 'john'
        self.password = '123'
        user = User.objects.create_user(username=self.username, email='john@doe.com', password=self.password)
        self.topic = Topic.objects.create(subject='Hello, world', board=self.board, starter=user)
        Post.objects.create(message='Lorem ipsum dolor sit amet', topic=self.topic, created_by=user)
        self.url = reverse('reply_topic', kwargs={'id': self.board.id, 'topic_id': self.topic.id})

# boards/tests/test_login_required_reply_topic_tests.py
from django.contrib.auth.models import User
from django.test import TestCase
from django.urls import reverse
from ..models import Board, Post, Topic
from ..views import reply_topic
from .test_reply_topic_test_case import ReplyTopicTestCase


class LoginRequiredReplyTopicTests(ReplyTopicTestCase):
    def test_redirection(self):
        login_url = reverse("login")
        response = self.client.get(self.url)
        self.assertRedirects(
            response, "{login_url}?next={url}".format(login_url=login_url, url=self.url)
        )

# boards/tests/test_reply_topic_tests.py
from django.contrib.auth.models import User
from django.test import TestCase
from django.urls import reverse, resolve
from ..models import Board, Post, Topic
from ..views import reply_topic
from .test_reply_topic_test_case import ReplyTopicTestCase
from ..forms import PostForm

class ReplyTopicTests(ReplyTopicTestCase):
    def setUp(self):
        super().setUp()
        self.client.login(username=self.username, password=self.password)
        self.response = self.client.get(self.url)

    def test_status_code(self):
        self.assertEqual(self.response.status_code, 200)

    def test_view_function(self):
        view = resolve('/boards/1/topics/1/reply/')
        self.assertEqual(view.func, reply_topic)

    def test_csrf(self):
        self.assertContains(self.response, 'csrfmiddlewaretoken')

    def test_contains_form(self):
        form = self.response.context.get('form')
        self.assertIsInstance(form, PostForm)

    def test_form_inputs(self):
        '''
        The view must contain two inputs: csrf, message textarea
        '''
        self.assertContains(self.response, '<input', 1)
        self.assertContains(self.response, '<textarea', 1)

# boards/tests/test_successful_reply_topic_tests.py
from django.contrib.auth.models import User
from django.test import TestCase
from django.urls import reverse
from ..models import Board, Post, Topic
from ..views import reply_topic
from .test_reply_topic_test_case import ReplyTopicTestCase

class SuccessfulReplyTopicTests(ReplyTopicTestCase):
    def setUp(self):
        super().setUp()
        self.client.login(username=self.username, password=self.password)
        self.response = self.client.post(self.url, {'message': 'hello, world!'})

    def test_redirection(self):
        '''
        A valid form submission should redirect the user
        '''
        topic_posts_url = reverse('topic_posts', kwargs={'id': self.board.id, 'topic_id': self.topic.id})
        self.assertRedirects(self.response, topic_posts_url)

    def test_reply_created(self):
        '''
        The total post count should be 2
        The one created in the `ReplyTopicTestCase` setUp
        and another created by the post data in this class
        '''
        self.assertEqual(Post.objects.count(), 2)

# boards/tests/test_invalid_reply_topic_tests.py
from django.contrib.auth.models import User
from django.test import TestCase
from django.urls import reverse
from ..models import Board, Post, Topic
from ..views import reply_topic
from .test_reply_topic_test_case import ReplyTopicTestCase

class InvalidReplyTopicTests(ReplyTopicTestCase):
    def setUp(self):
        '''
        Submit an empty dictionary to the `reply_topic` view
        '''
        super().setUp()
        self.client.login(username=self.username, password=self.password)
        self.response = self.client.post(self.url, {})

    def test_status_code(self):
        '''
        An invalid form submission should return to the same page
        '''
        self.assertEqual(self.response.status_code, 200)

    def test_form_errors(self):
        form = self.response.context.get('form')
        self.assertTrue(form.errors)

The crux here is the ReplyTopicTestCase class. The other four test cases extend the ReplyTopicTestCase class.

First, I check if the view is protected with the @login_required decorator, and then check the HTML inputs, status code. Finally, I test a valid and an invalid form submission.

A QuerySet represents a collection of objects from my database. It can have zero, one, or many filters. QuerySets reduce the number of query results based on given parameters. In SQL terms, a QuerySet equates to a SELECT statement, and a filter is a limiting clause such as WHERE or LIMIT.

I get a QuerySet by using my model’s Manager. Each model has at least one Manager, and it’s called objects by default. I can access it directly via the model class. For example:

Blog.objects
django.db.models.manager.Manager object at ...>
b = Blog(name="Foo", tagline="Bar")
b.objects
Traceback:
    ...
AttributeError: "Manager isn't accessible via Blog instances."

To learn more about QuerySets, please visit Making queries in the official Django documentation.

I have three things to add to the index/home view:

1. Display the posts count of the board.
2. Display the topics count of the board.
3. Display the last user who posted something and the date and time it was posted.

But let's first experiment with the Python shell for a bit before refactoring the index/home view.

Before I start experimenting with the Python shell, let's add the following to the Post model (at the end):

from django.utils.text import Truncator # new

def __str__(self):
    truncated_message = Truncator(self.message)  # new
    return truncated_message.chars(30) # new
    # return self.message

Above, I am using the Truncator utility class. It truncates long strings into an arbitrary string size. Here it is 30 characters.

To start the Python shell, I run the following command in Terminal:

python3 manage.py shell

And for me, the following is returned:

Python 3.12.5 (main, Aug 26 2024, 07:35:37) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)

Then, let's run the following:

# first import Board model
from boards.models import Board
# then get a board instance from the database
board = Board.objects.get(name='Django')
# then get the board topics QuerySet:
board.topics.all()
# which returns:
<QuerySet [<Topic: Explain the Django directory structure>, <Topic: A new Django topic>]>
# then get the board topics count:
board.topics.count()
# which returns:
2

Next, let's get the number of posts within a board:

# first import the Post model:
from boards.models import Post
# then get the board posts QuerySet:
Post.objects.all()
# which returns:
<QuerySet [<Post: I'm so glad someone started a…>, <Post: I am really excited about sta…>, <Post: I am writing my first new top…>, <Post: I am writing my first new top…>, <Post: I am writing my first new top…>, <Post: This is my first post topic. …>, <Post: My other new topic.>, <Post: This is my new_topic so I can…>, <Post: This is an entirely new topic…>, <Post: Hey there. Great post topic!>, <Post: I love your post topic too!>]>
# then get the total number of posts:
Post.objects.count()
# which returns:
11

I have a total of 11 posts, but they don't necessarily all belong to the Django board. However, I can filter the posts:

Post.objects.filter(topic__board=board)
# which returns:
<QuerySet [<Post: I'm so glad someone started a…>, <Post: I am really excited about sta…>]>
# filter out the Django topic posts:
Post.objects.filter(topic__board=board).count()
# which returns:
2

In my case, Django returned the same two posts in the QuerySet as well as the count(). That is because I had previously defined the board, which was Django, and I only have two Django topics.

I use double underscores in topic__board to navigate through the models’ relationships. Under the hood, Django builds a connection between Board -> Topic -> Post, and builds an SQL query to retrieve just the posts that belong to a specific board.

Lastly, I want to identify the latest post:

# order by the `created_at` field, getting the most recent post first:
Post.objects.filter(topic__board=board).order_by('-created_at')
# which returns:
<QuerySet [<Post: I am really excited about sta…>, <Post: I'm so glad someone started a…>]>
# then we can use the `first()` method to just grab the result that interests us:
Post.objects.filter(topic__board=board).order_by('-created_at').first()
# which returns:
<Post: I am really excited about sta…>

Now I can implement what I just did in the Python shell in my actual code.

# boards/models.py
class Board(models.Model):
    name = models.CharField(max_length=30, unique=True)
    description = models.CharField(max_length=100)

    def __str__(self):
        return self.name

    def get_posts_count(self): # new
        return Post.objects.filter(topic__board=self).count()

    def get_latest_post(self): # new
        return Post.objects.filter(topic__board=self).order_by('-created_at').first()

I am using self, because the methods are used by a Board instance. I am using the Board instance to filter the QuerySet.

<!-- templates/index.html -->
{% extends "base.html" %}
{% block breadcrumb %}
  <li class="breadcrumb-item active">Boards</li>
{% endblock breadcrumb %}
{% block content %}
  <table class="table">
    <thead class="thead-inverse">
      <tr>
        <th>Board</th>
        <th>Posts</th>
        <th>Topics</th>
        <!-- new wording (instead of Last Post) -->
        <th>Latest Post</th>
      </tr>
    </thead>
    <tbody>
      {% for board in boards %}
        <tr>
          <td>
            <a href="{% url 'board_topics' board.id %}">{{ board.name }}</a>
            <small class="text-muted d-block">{{ board.description }}</small>
          </td>
          <td class="align-middle">{{ board.get_posts_count }}</td>
          <td class="align-middle">{{ board.topics.count }}</td>
          <td class="align-middle">
            {% if board.get_posts_count > 0 %}
              {% with post=board.get_latest_post %}
                <small>
                  <a href="{% url 'topic_posts' board.id post.topic.id %}">By {{ post.created_by.username }} at {{ post.created_at }}</a>
                </small>
              {% endwith %}
            </td>
          {% else %}
            <small>0</small>
          </tr>
        {% endif %}
      {% endfor %}
    </tbody>
  </table>
{% endblock content %}

I also included an if statement regarding getting the latest post, because it could be the case that a board has no topics and no posts. So the if statement checks if there indeed is at least one board topic post, and if so, render a link to that latest post. Otherwise, just render 0 to indicate that there is no latest post to link to.

I could also do something a bit more verbose:

<!-- templates/index.html -->
{% extends "base.html" %}
{% block breadcrumb %}
  <li class="breadcrumb-item active">Boards</li>
{% endblock breadcrumb %}
{% block content %}
  <table class="table">
    <thead class="thead-inverse">
      <tr>
        <th>Board</th>
        <th>Posts</th>
        <th>Topics</th>
        <th>Latest Post</th>
      </tr>
    </thead>
    <tbody>
      {% for board in boards %}
        <tr>
          <td>
            <a href="{% url 'board_topics' board.id %}">{{ board.name }}</a>
            <small class="text-muted d-block">{{ board.description }}</small>
          </td>
          <td class="align-middle">{{ board.get_posts_count }}</td>
          <td class="align-middle">{{ board.topics.count }}</td>
          <td class="align-middle">
            {% with post=board.get_latest_post %}
              {% if post %}
                <small>
                  <a href="{% url 'topic_posts' board.id post.topic.id %}">By {{ post.created_by.username }} at {{ post.created_at }}</a>
                </small>
              {% else %}
                <small class="text-muted"><em>No posts yet.</em></small>
              {% endif %}
            {% endwith %}
          </td>
        </tr>
      {% endfor %}
    </tbody>
  </table>
{% endblock content %}

Either works just fine. It's a matter of personal preference. The second approach looks like the following in the browser:

Adding posts count, topics count, last post to index/home view approach 2

I am going to go with the first approach, and am going to create a new Random Board topic:

Adding a new Random board topic

The new Random board topic link takes me to the following:

New Random board topic

python3 manage.py test results in the following:

Found 65 test(s).
Creating test database for alias 'default'...
System check identified no issues (0 silenced).
EEEEE..............F...................................FF.F......
======================================================================
FAIL: test_csrf (accounts.tests.test_password_reset_confirm_tests.PasswordResetConfirmTests.test_csrf)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/mariacam/Python-Development/django-boards/django_boards/accounts/tests/test_password_reset_confirm_tests.py", line 36, in test_csrf
    self.assertContains(self.response, 'csrfmiddlewaretoken')
  File "/Users/mariacam/.pyenv/versions/3.12.5/lib/python3.12/site-packages/django/test/testcases.py", line 623, in assertContains
    self.assertTrue(
AssertionError: False is not true : Couldn't find 'csrfmiddlewaretoken' in the following response
b'\n<!DOCTYPE html>\n<html lang="en">\n  <head>\n    <meta charset="utf-8">\n    <meta name="description" content="A forum dedicated to all things Django" />\n    <meta name="keywords" content="django, python3" />\n    <title>\n      \n  \n    Reset your password\n  \n\n    </title>\n    <link rel="stylesheet" href="/static/css/bootstrap.min.css">\n    <link rel="stylesheet" href="/static/css/app.css">\n    \n  <link rel="stylesheet" href="/static/css/accounts.css">\n\n  </head>\n  <body>\n    \n  <div class="container">\n    <h1 class="text-center logo my-4">\n      <a href="/">Django Boards</a>\n    </h1>\n    \n  <div class="row justify-content-center">\n    <div class="col-lg-6 col-md-8 col-sm-10">\n      <div class="card">\n        <div class="card-body">\n          \n            <h3 class="card-title">Reset your password</h3>\n            <div class="alert alert-danger" role="alert">\n              It looks like you clicked on an invalid password reset link. Please try again.\n            </div>\n            <a href="/password-reset/" class="btn btn-secondary btn-block">Request a new password reset link</a>\n          \n        </div>\n      </div>\n    </div>\n  </div>\n\n  </div>\n\n    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/2.9.2/umd/popper.min.js"\n            integrity="sha512-2rNj2KJ+D8s1ceNasTIex6z4HWyOnEYLVC3FigGOmyQCZc2eBXKgOxQmo3oKLHyfcj53uz4QMsRCWNbLd32Q1g=="\n            crossorigin="anonymous"\n            referrerpolicy="no-referrer"></script>\n    <script src="https://code.jquery.com/jquery-3.7.1.min.js"\n            integrity="sha256-/JqT3SQfawRcv/BIHPThkBvs0OEvtFFmqPF/lYI/Cxo="\n            crossorigin="anonymous"></script>\n    <script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap/5.3.3/js/bootstrap.min.js"\n            integrity="512-ykZ1QQr0Jy/4ZkvKuqWn4iF3lqPZyij9iRv6sGqLRdTPkY69YX6+7wvVGmsdBbiIfN/8OdsI7HABjvEok6ZopQ=="\n            crossorigin="anonymous"\n            referrerpolicy="no-referrer"></script>\n  </body>\n</html>\n'

======================================================================
FAIL: test_csrf (boards.tests.test_new_topic_tests.NewTopicTests.test_csrf)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/mariacam/Python-Development/django-boards/django_boards/boards/tests/test_new_topic_tests.py", line 18, in test_csrf
    self.assertContains(response, 'csrfmiddlewaretoken')
  File "/Users/mariacam/.pyenv/versions/3.12.5/lib/python3.12/site-packages/django/test/testcases.py", line 609, in assertContains
    text_repr, real_count, msg_prefix, content_repr = self._assert_contains(
                                                      ^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/mariacam/.pyenv/versions/3.12.5/lib/python3.12/site-packages/django/test/testcases.py", line 571, in _assert_contains
    self.assertEqual(
AssertionError: 302 != 200 : Couldn't retrieve content: Response code was 302 (expected 200)

======================================================================
FAIL: test_new_topic_invalid_post_data (boards.tests.test_new_topic_tests.NewTopicTests.test_new_topic_invalid_post_data)
Invalid post data should not redirect
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/mariacam/Python-Development/django-boards/django_boards/boards/tests/test_new_topic_tests.py", line 37, in test_new_topic_invalid_post_data
    self.assertEqual(response.status_code, 200)
AssertionError: 302 != 200

======================================================================
FAIL: test_new_topic_valid_post_data (boards.tests.test_new_topic_tests.NewTopicTests.test_new_topic_valid_post_data)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/mariacam/Python-Development/django-boards/django_boards/boards/tests/test_new_topic_tests.py", line 27, in test_new_topic_valid_post_data
    self.assertTrue(Topic.objects.exists())
AssertionError: False is not true

----------------------------------------------------------------------
Ran 65 tests in 9.403s

FAILED (failures=4)
Destroying test database for alias 'default'...

However, if I want to know how my latest tests in particular pass, I can run them individually. Let's do that!

Running test_login_required_reply_topic_tests.py:

python3 manage.py test boards.tests.test_login_required_reply_topic_tests

Returns the following:

Found 1 test(s).
Creating test database for alias 'default'...
System check identified no issues (0 silenced).
.
----------------------------------------------------------------------
Ran 1 test in 0.231s

OK
Destroying test database for alias 'default'...

Running test_reply_topic_tests.py:

python3 manage.py test boards.tests.test_reply_topic_tests

Returns the following:

Found 5 test(s).
Creating test database for alias 'default'...
System check identified no issues (0 silenced).
..F..
======================================================================
FAIL: test_form_inputs (boards.tests.test_reply_topic_tests.ReplyTopicTests.test_form_inputs)
The view must contain two inputs: csrf, message textarea
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/mariacam/Python-Development/django-boards/django_boards/boards/tests/test_reply_topic_tests.py", line 33, in test_form_inputs
    self.assertContains(self.response, '<input', 1)
  File "/Users/mariacam/.pyenv/versions/3.12.5/lib/python3.12/site-packages/django/test/testcases.py", line 614, in assertContains
    self.assertEqual(
AssertionError: 2 != 1 : Found 2 instances of '<input' (expected 1) in the following response
b'\n<!DOCTYPE html>\n<html lang="en">\n  <head>\n    <meta charset="utf-8">\n    <meta name="description" content="A forum dedicated to all things Django" />\n    <meta name="keywords" content="django, python3" />\n    <title>\n      \n  Post a reply\n\n    </title>\n    <link rel="stylesheet" href="/static/css/bootstrap.min.css">\n    <link rel="stylesheet" href="/static/css/app.css">\n    \n    \n  </head>\n  <body>\n    \n      <nav class="navbar navbar-expand-sm navbar-dark bg-dark">\n        <div class="container">\n          <a class="navbar-brand" href="/">Django Boards</a>\n          \n            <div class="dropdown">\n              <a class="btn btn-primary dropdown-toggle"\n                 href="#"\n                 role="button"\n                 data-bs-toggle="dropdown"\n                 aria-expanded="false">john</a>\n              <ul class="dropdown-menu">\n                <li>\n                  <a class="dropdown-item" href="#">My account</a>\n                </li>\n                <li>\n                  <a class="dropdown-item" href="#">change password</a>\n                </li>\n                <li>\n                  <form method="post" action="/logout/">\n                    <input type="hidden" name="csrfmiddlewaretoken" value="tLFxq0CcwZaJPWoOyXSo4rQVOT0YL67JqvergYZB28iqJYiMAFb4UUhAFolRVjxW">\n                    <button type="submit">Logout</button>\n                  </form>\n                </li>\n              </ul>\n            </div>\n            <button class="navbar-toggler"\n                    type="button"\n                    data-toggle="collapse"\n                    data-target="#mainMenu"\n                    aria-controls="mainMenu"\n                    aria-expanded="false"\n                    aria-label="Toggle navigation">\n              <span class="navbar-toggler-icon"></span>\n            </button>\n          \n        </div>\n      </nav>\n      <div class="container">\n        <ol class="breadcrumb my-4">\n          \n  <li class="breadcrumb-item">\n    <a href="/">Boards</a>\n  </li>\n  <li class="breadcrumb-item">\n    <a href="/boards/1/">Django</a>\n  </li>\n  <li class="breadcrumb-item">\n    <a href="/boards/1/topics/1/">Hello, world</a>\n  </li>\n  <li class="breadcrumb-item active">Post a reply</li>\n\n        </ol>\n        \n  <form method="post" class="mb-4">\n    <input type="hidden" name="csrfmiddlewaretoken" value="tLFxq0CcwZaJPWoOyXSo4rQVOT0YL67JqvergYZB28iqJYiMAFb4UUhAFolRVjxW">\n    \n\n\n\n\n  <div class="form-group">\n    <label for="id_message">Message:</label>\n    <textarea name="message" cols="40" rows="10" maxlength="4000" class="form-control " required id="id_message">\n</textarea>\n    \n    \n  </div>\n\n    <button type="submit" class="btn btn-success">Post a reply</button>\n  </form>\n  \n    <div class="card mb-2">\n      <div class="card-body p-3">\n        <div class="row mb-3">\n          <div class="col-6">\n            <div class="col-6">\n              <strong class="text-muted">john</strong>\n            </div>\n            <div class="col-6 text-right">\n              <small class="text-muted">Sept. 24, 2024, 12:42 a.m.</small>\n            </div>\n          </div>\n          <div class="mb-2 mt-3">Lorem ipsum dolor sit amet</div>\n        </div>\n        <div class="col-6 text-right">\n          <small>0 Likes</small>\n        </div>\n      </div>\n    </div>\n  \n\n      </div>\n    \n    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/2.9.2/umd/popper.min.js"\n            integrity="sha512-2rNj2KJ+D8s1ceNasTIex6z4HWyOnEYLVC3FigGOmyQCZc2eBXKgOxQmo3oKLHyfcj53uz4QMsRCWNbLd32Q1g=="\n            crossorigin="anonymous"\n            referrerpolicy="no-referrer"></script>\n    <script src="https://code.jquery.com/jquery-3.7.1.min.js"\n            integrity="sha256-/JqT3SQfawRcv/BIHPThkBvs0OEvtFFmqPF/lYI/Cxo="\n            crossorigin="anonymous"></script>\n    <script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap/5.3.3/js/bootstrap.min.js"\n            integrity="512-ykZ1QQr0Jy/4ZkvKuqWn4iF3lqPZyij9iRv6sGqLRdTPkY69YX6+7wvVGmsdBbiIfN/8OdsI7HABjvEok6ZopQ=="\n            crossorigin="anonymous"\n            referrerpolicy="no-referrer"></script>\n  </body>\n</html>\n'

----------------------------------------------------------------------
Ran 5 tests in 2.140s

FAILED (failures=1)
Destroying test database for alias 'default'...

Remember these errors from other instances of the test_form_inputs function and status code 302 != 200 fails? I will implement Beautiful Soup 4 and Soup Sieve again to ensure that these tests pass instead of hard coding the arguments passed to assertContains().

Running test_successful_reply_topic_tests.py:

python3 manage.py test boards.tests.test_successful_reply_topic_tests

Returns the following:

Found 2 test(s).
Creating test database for alias 'default'...
System check identified no issues (0 silenced).
..
----------------------------------------------------------------------
Ran 2 tests in 0.865s

OK
Destroying test database for alias 'default'...

Running test_invalid_reply_topic_tests.py:

python3 manage.py test boards.tests.test_invalid_reply_topic_tests

Returns the following:

 python3 manage.py test boards.tests.test_invalid_reply_topic_tests
Found 2 test(s).
Creating test database for alias 'default'...
System check identified no issues (0 silenced).
..
----------------------------------------------------------------------
Ran 2 tests in 0.896s

OK
Destroying test database for alias 'default'...

I will go through debugging the (current) failed tests in Part 20. There are five failed tests, including the test_reply_topic_tests.py file. The test failures are all familiar.

I will include the topic replies (posts) count in a different way, and I'll test it out first in the Python shell:

from django.db.models import Count
from boards.models import Board

board = Board.objects.get(name='Django')
topics = board.topics.order_by('-last_updated').annotate(replies=Count('posts'))

for topic in topics:
    print(topic.replies)

# which, for me, returns:
1
1
1
3
1
1
1