Matt Segal Dev

How to customise a class based view in Django
Thu 09 April 2020, by Matthew Segal
Category: Django

You've spend a little bit of time working on your Django app and you want to dip your toes into class-based views. The basic examples are simple enough, but once you want to do something more complicated, something more custom, you get stuck. How do you customise a class-based view?

You've written some function-based views before, and they seem pretty straightforward, it's just a function! If you want to change how it works, you just change the code inside the function. Simple - no magic, no mystery, it's just code. Customising class based views seems much less user-friendly.

In this post I'll take you through a worked example, showing you how to customise class-based views.

Example problem

Let's start with an example problem. Say we've got a model called Article, used for publishing news online:

# models.py

class Article(models.Model):

    created_at = models.DateTimeField(default=timezone.now)
    published_at = models.DateTimeField(blank=True, null=True)
    title = models.CharField(max_length=512)
    body_html = models.TextField()

We have a function-based view that lists all the articles:

# views.py

def article_list_view(request):
    articles = Article.objects.all()
    context = {'articles': articles}
    return render(request, 'news/article_list.html', context)

As I mentioned earlier, this function-based code is pretty easy to customise - you just change the code! Let's say we only want to list all the published articles and list them from newest to oldest:

# views.py

def article_list_view(request):
    articles = (
        Article.objects
        .filter(published_at__isnull=False)
        .order_by('-published_at')
    )
    context = {'object_list': articles}
    return render(request, "news/article_list.html", context)

Now let's try doing the same thing with a class-based view. Listing all Articles is super simple. It's like 3 lines of code:

# views

class ArticleListView(ListView):
    model = Article
    template_name = "news/article_list.html"

Cool, cool, and now we need to do the next bit: list all the published articles and list them from newest to oldest. How the fuck do we do that? Where do you even start? Are you stressed? I'm stressed.

The fix

The fix is to read some documentation. Not the Django docs, which are great for a lot of topics. No, you are going to need to refer to Classy Class-Based Views to keep your sanity. Let's take a peek at the documentation for ListView.

I'm going to cut to video to show you the rest of the fix.

You can use the techniques of overriding on any of the class-based view methods, depending on what you need to do.

A common method to override is get_context_data:

class ArticleListView(ListView):
    model = Article
    template_name = "news/article_list.html"

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        return {
            **context,
            'now': timezone.now()
        }

In summary, when you're stuck on a class-based view:

If you have any feedback or questions email me at [email protected]