class BookDetailView(DetailView):
    model = Book
    slug_field = 'url'
    slug_url_kwarg = 'url'

    def get_context_data(self, *args, **kwargs):
        context = super().get_context_data(*args, **kwargs)
        context['title'] = Book.objects.filter(url=self.kwargs['url']).first()
        return context

    def cart_book_form(request):
        cart_book_form = CartAddBookForm()
        return render(request, 'catalog/detail.html', {'book': book, 'cart_book_form': cart_book_form})