Question

I had a many-to-many relationship between two Django Models:

from django.contrib.auth.models import User
class UserProfile(models.Model):
    user = models.OneToOneField(User)
    ...
    bees = models.ManyToManyField('Bee')
class Bee(models.Model):
    ...

in my template, I want to have a different output depending on whether the user has certain Bees. What I’m doing right now is to create a custom filter that does something resembling this:

@register.filter
def my_filter(user, bee):
    userprofile = user.get_profile()
    return bee in userprofile.bees.all()

and in the template, I can use it as such:

{% for bee in bees %}
    {% if user|my_filter:bee %}
        I am in {{ bee }}
    {% else %}
        I am not in {{ bee }}
    {% endif %}
{% endfor %}

but this seems hackish since 1) I called .all() — loading the all Bees including the bees that I’m not interested in — without using the results, 2) I don’t think I should need to create a custom filter as this should be quite common

What is the proper way to check whether a Model belongs to a many-to-many relationship with another Model?

Answer 1

You could get the list of the user’s bee ids in your view. Something like this:

def view(request):
    user_bee_ids = request.user.bees.all().values_list('pk', flat=True)

And then in your template you can do this:

{% if bee.pk in user_bee_ids %}
    I am in {{ bee }}
{% else %}
    I am not in {{ bee }}
{% endif %}