When and how to use Django ListView

When to use ListView?

Django provides several class based generic views to accomplish common tasks. One among them is ListView.

Most basic class based generic view is TemplateView. We wrote about it in our last post.

ListView should be used when you want to present a list of objects in a html page.

ListView shouldn’t be used when your page has forms and does creation or update of objects. FormView, CreateView and UpdateView are more suitable for working with forms, creation or updation of objects.

TemplateView can achieve everything which ListView can, but ListView has an advantage of avoiding a lot of boilerplate code which would be needed with TemplateView.

Let’s write a view using base view View and then modify it to use TemplateView and then to use ListView. ListView would help us avoid several lines of code and would also provide better separation of concern.

Vanilla View

Assume there is a model called Book which looks like:

class Book(models.Model):
    name = models.CharField(max_length=100)
    author_name = models.CharField(max_length=100)

We want to have a page which shows all the books in the database. View would look like:

class BookListView(View):

	def get(self, request, *args, **kwargs):
		books = Book.objects.all()
		context = {'books': books}
		return render(request, "book-list.html", context=context)

book-list.html looks like the following:

By subclassing TemplateView

class BookListView(TemplateView):
	template_name = 'book-list.html'

	def get_context_data(self, *args, **kwargs):
		context = super(BookListView, self).get_context_data(*args, **kwargs)
		context['books'] = Book.objects.all()
		return context

As discussed in last post on TemplateView, we didn’t have to provide a get() implementation and didn’t have to bother with render() while using TemplateView. All that was taken care of by TemplateView.

We only had to provide a get_context_data() implementation to add context to the template.

By subclassing ListView

from django.views.generic.list import ListView

class BookListView(ListView):
	template_name = 'book-list.html'
	queryset = Book.objects.all()
	context_object_name = 'books'

ListView removes more boilerplate from TemplateView. With ListView we didn’t have to bother with get_context_data() implementation. ListView takes care of creating context variable ‘books’ and passing this context variable to template.

We can also add filtering in ListView.queryset.

class BookListView(ListView):
	template_name = 'book-list.html'
	queryset = Book.objects.filter(name='A Feast for Crows')
	context_object_name = 'books'

Had we wanted pagination, we would have had to add several lines of code in TemplateView or vanilla View implementation. ListView provides pagination for free, we don’t have to add pagination code.

Pagination can be added to ListView subclasses by setting a variable paginate_by

class BookListView(ListView):
	template_name = 'book-list.html'
	queryset = Book.objects.all()
	context_object_name = 'books'
	paginate_by = 10

After this /books-list/?page=1 will return first 10 books. /books-list/?page=2 will return next 10 books and so on.

Further configuring ListView

If your list page’s queryset doesn’t need any filtering, and works with .all() on your model, then you can provide a model attribute on the BookListView instead of providing queryset.

class BookListView(ListView):
	template_name = 'book-list.html'
	model = Book
	context_object_name = 'books'
	paginate_by = 10

You can add ordering to your queryset by adding ordering attribute on View. Suppose you want the books to be ordered in the page by their created date descending. You can do:

class BookListView(ListView):
	template_name = 'book-list.html'
	model = Book
	context_object_name = 'books'
	paginate_by = 10
	ordering = ['-created']

Since ordering is a list, so you can order by multiple attributes.

In case you want to filter the queryset differently for different web requests, then you can skip adding model or queryset on the list view and instead provide a get_queryset() implementation.

class BookListView(ListView):
	template_name = 'book-list.html'
	context_object_name = 'books'
	paginate_by = 10
	ordering = ['-created']

    def get_queryset(self):
        return Book.objects.filter(created_by=self.request.user)

You can avoid template_name attribute too. The default behaviour of ListView is to use a template with name <app-label>/<model-name>_list.html. You can change your BookListView to look like:

class BookListView(ListView):
	model = Book
	context_object_name = 'books'
	paginate_by = 10

But then your template code should be in books/book_list.html. This assumes that your Book model is in app books. In case Book model is in, say entitites app, then template code should be in entities/book_list.html.

You can avoid context_object_name too. The default behaviour of ListView is to populate the template with context name object_list. You can change your BookListView to look like:

class BookListView(ListView):
	model = Book
	paginate_by = 10

In such case your template code should change to:

Essentially a ListView helps you avoid boilerplate code like:

  • providing a GET() implementation.
  • Creating queryset with ordering.
  • providing an encapsulated pagination code. Had we written pagination code in vanilla view, it would have easily added more 10 lines of code.
  • providing the template with a sane context.
  • creating and returning a HttpResponse() or a subclass of HttpResponse() object.

The must requirement for a ListView is, it must be provided with a model or queryset or a get_queryset() implementation. Every other piece has a sane default.

Thank you for reading the Agiliq blog. This article was written by akshar on Dec 29, 2017 in django .

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