Use object variable in base.html of Django - django

Question

I come from Ruby on Rails and I am trying to learn Django. There are multiple things that puzzle me when it comes to how to solve simple things. I have a sidebar in which I would like to have a link to a random item.
My first thought was to use:
Random headline
Although it works perfectly fine to run Headline.objects.order_by('?')[0].id in the shell, this causes an error in Django:
Could not parse the remainder: '('?')[0].id' from 'Headline.objects.order_by('?')[0].id'
which I find very weird since 'Headline.objects.order_by('?')[0].id' creates a number (id) and if I put the same number in as
Random headline
it works perfectly fine.
Another option would be to create this previously in the template, like
{% rand_id = Headline.objects.order_by('?')[0].id %}
Random headline
which is I would hotfix it in Rails - but this doesn't work. The third option (which is better than the 2nd) is to put the variable in the view. However, this is not really viable since this code is in the sidebar and I cannot pass this in every view (DRY!).
So, I figure out I should use context templates, which I - after reading up on it find overly complicated for something as simple as this.
Is there really no good, simple way to solve this problem? Or am I "thinking too much rails"?

Answer 1

In your case a custom template tag would be just fine.
https://docs.djangoproject.com/en/4.0/howto/custom-template-tags/#writing-custom-template-tags
from django import template
from django.utils.html import format_html
register = template.Library()
#register.simple_tag
def random_headline_link():
random_headline = Headline.objects.order_by('?')[0]
headline_url = reverse('headline_detail', args=[random_headline.id,])
return format_html('Random headline', url=headline_url)
{% random_headline_link %}
<!-- the rest is not needed anymore, as it is all coupled together in the templatetag -->
Or if you only like/need the URL, you could use the following templatetag code.
from django import template
register = template.Library()
#register.simple_tag
def random_headline_url():
random_headline = Headline.objects.order_by('?')[0]
return reverse('headline_detail', args=[random_headline.id,])
Random headline