Question

I have the following models:

class Post(models.Model):
    message = models.TextField()
    (etc.)

class UserProfile(models.Model):
    user = models.ForeignKey(User, unique=True)
    (etc.)

class PostFollow(models.Model):
    post = models.ForeignKey(Post, related_name='follower_set')
    follower = models.ForeignKey(UserProfile, related_name='follower_set')
    creation_date = models.DateTimeField(auto_now_add=True)
    an_arbitrary_score = models.IntegerField(default=0)
    (etc.)

    class Meta:
        unique_together = ('post', 'follower',)

In my template, I’d like to render a list of posts along with a “follow” or “unfollow” link so that the current user can decide whether to follow a given post. In a world where I could use arguments in Django templating, I’d do something like this:

{% for post in post_set %}
    <...stuff...>
    {% if post.user_is_following user %}unfollow{% else %}follow{% endif %}
    <...more stuff...>
{% endfor %}

However, I can’t do that. And I can’t make a zero-argument, template-callable method on any of these models, because they all need to know at least one other argument to answer the question whether a given PostFollow row exists in that table.

I’m happy to write a templating extension, but before I bring out the big guns, is this an appropriate case for doing so? Or is there a more Djangoesque solution?

Answer 1

Template filters are not big guns:

# your_app/templatetags/following.py 

from django import template
register = template.Library()

@register.filter
def is_followed_by(post, user):
   return post.is_followed_by(user)  

and then:

{% load following %}
...
{% if post|is_followed_by:user %} ... {% endif %}

You can also put all logic in template filter, remove ‘post.is_followed_by’ method and use the filter instead of model method just like any other function, @register.filter decorator doesn’t harm the decorated function.