More Views

Blogs should be interactive. Let’s allow visitors to comment on each entry.

Adding a Comment model

First we need to add a Comment model in blog/models.py.

class Comment(models.Model):
    entry = models.ForeignKey(Entry)
    name = models.CharField(max_length=100)
    email = models.EmailField()
    body = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True, editable=False)
    modified_at = models.DateTimeField(auto_now=True, editable=False)

Since we have added a new model, we also need to make sure that this model gets synced to our SQLite database.

$ python manage.py makemigrations
Migrations for 'blog':
  0002_auto_20141019_0232.py:
    - Create model Comment
    - Change Meta options on entry
$ python manage.py migrate
Operations to perform:
  Apply all migrations: contenttypes, blog, admin, auth, sessions
Running migrations:
  Applying blog.0002_auto_20141019_0232... OK

Before we create a __str__ method for our Comment model similar to the one we previously added for our Entry model, let’s create a test in blog/tests.py.

Our test should look very similar to the __str__ test we wrote in EntryModelTest earlier. This should suffice:

class CommentModelTest(TestCase):

    def test_string_representation(self):
        comment = Comment(body="My comment body")
        self.assertEqual(str(comment), "My comment body")

Don’t forget to import our Comment model:

from .models import Entry, Comment

Now let’s run our tests to make sure our new test fails:

$ python manage.py test blog

Creating test database for alias 'default'...
F..........
======================================================================
FAIL: test_string_representation (blog.tests.CommentModelTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  ...
AssertionError: 'Comment object' != 'My comment body'
- Comment object
+ My comment body


----------------------------------------------------------------------
Ran 11 tests in 0.154s

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

Great. So it looks like our test fails. Now we should implement the __str__ method for the comment body, an exercise we leave to the reader. After implementing the method, run the test again to see it pass:

$ python manage.py test blog

Creating test database for alias 'default'...
...........
----------------------------------------------------------------------
Ran 11 tests in 0.085s

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

Adding comments on the admin site

Let’s add the Comment model to the admin just like we did with the Entry model. This involves editing blog/admin.py to look like this:

from django.contrib import admin

from .models import Entry, Comment


admin.site.register(Entry)
admin.site.register(Comment)

If you start the development server again, you will see the Comment model in the admin and you can add comments to the blog entries. However, the point of a blog is to let other users and not only the admin post comments.

Displaying comments on the website

Now we can create comments in the admin interface, but we can’t see them on the website yet. Let’s display comments on the detail page for each blog entry.

After the <hr> element inside of our content block in templates/blog/entry_detail.html let’s add the following:

<hr>
<h4>Comments</h4>
{% for comment in entry.comment_set.all %}
    <p><em>Posted by {{ comment.name }}</em></p>
    {{ comment|linebreaks }}
{% empty %}
    No comments yet.
{% endfor %}

Important

We forgot to add tests for this! Why don’t you add a test to make sure comments appear on the blog entry page and a test to make sure the “No comments yet” message shows up appropriately. These tests should probably be added to our EntryViewTest class.

Now we can see our comments on the website.