How to declare common variables for all methods of a Django class-based view?

Question

I have a class-based view in my Django application and it works fine. But I guess it is not coded well, because it violates the DRY principle. Specifically, I have two absolutely similar declarations of the posts_list variable inside get() and post() methods:

class TopicView(View):
    def get(self, request, topic_id):
        post_form = PostForm()
        posts_list = Post.objects.filter(topic_id=self.kwargs['topic_id']).order_by('-creation_date')
        return render(request, 'discussions/topic.html', {'posts_list': posts_list,
                                                          'post_form': post_form,
                                                          'topic_id': topic_id})

    def post(self, request, topic_id):
        post_form = PostForm(request.POST)

        if post_form.is_valid():
            post = post_form.save(commit=False)
            post.author = request.user
            post.topic = Topic.objects.get(pk=topic_id)
            post.save()
            return redirect('discussions:topic', topic_id=topic_id)

        posts_list = Post.objects.filter(topic_id=self.kwargs['topic_id']).order_by('-creation_date')
        return render(request, 'discussions/topic.html', {'posts_list': posts_list,
                                                          'post_form': post_form,
                                                          'topic_id': topic_id})

Is there a way how I can declare this variable as a class attribute instead of a simple variable inside each of the methods? When I declaring it, I use topic_id as a filter for objects, and I extract topic_id from the URL (self.kwargs object, self is passed to both get() and post() as an input parameter). This is the main issue.

little_birdie · Accepted Answer · 2020-04-11 16:37:37Z

1

There are a few ways you can reorganize this. But one simple way is to put the common code in its own method, then call it when you need it.. like so:

class TopicView(View):
    def get(self, request, topic_id):
        return self.post_list_response(PostForm())

    def post(self, request, topic_id):
        post_form = PostForm(request.POST)

        if post_form.is_valid():
            post = post_form.save(commit=False)
            post.author = request.user
            post.topic = Topic.objects.get(pk=topic_id)
            post.save()
            return redirect('discussions:topic', topic_id=topic_id)

        return self.post_list_response(post_form)

    def post_list_response(self, post_form):
        topic_id = self.kwargs['topic_id']
        posts_list = Post.objects.filter(topic_id=topic_id).order_by('-creation_date')
        return render(request, 'discussions/topic.html', {
            'posts_list': posts_list,
            'post_form': post_form,
            'topic_id': topic_id
        })

You could also structure this slightly better/differently by using Django's FormView class rather than just plain View.

edited Apr 11, 2020 at 16:37

answered Apr 11, 2020 at 16:03

little_birdie

5,9273 gold badges26 silver badges32 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

kohek Over a year ago

Can I pass additional parameters to the template when using FormView? Namely, I mean posts_list variable which I need to have in my topic.html template.

little_birdie Over a year ago

Yes, with FormView, you can override FormView's get_context_data method to add your own context variables. You don't call render yourself, FormView does that for you.

little_birdie Over a year ago

Let me add.. with a FormView you would not implement get or post methods you just need a form_valid method which contains the code you want to run when the form is valid.. and then you would extend get_context_data to add the code for your list

Collectives™ on Stack Overflow

How to declare common variables for all methods of a Django class-based view?

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related