Given a model with ForeignKeyField (FKF) or ManyToManyField (MTMF) fields with a foreignkey to 'self' how can I prevent self (recursive) selection within the Django Admin (admin).
In short, it should be possible to prevent self (recursive) selection of a model instance in the admin. This applies when editing existing instances of a model, not creating new instances.
For example, take the following model for an article in a news app;
class Article(models.Model):
title = models.CharField(max_length=100)
slug = models.SlugField()
related_articles = models.ManyToManyField('self')
If there are 3 Article
instances (title: a1-3), when editing an existing Article
instance via the admin the related_articles
field is represented by default by a html (multiple)select box which provides a list of ALL articles (Article.objects.all()
). The user should only see and be able to select Article
instances other than itself, e.g. When editing Article
a1, related_articles
available to select = a2, a3.
I can currently see 3 potential to ways to do this, in order of decreasing preference;
- Provide a way to set the queryset providing available choices in the admin form field for the
related_articles
(via an exclude query filter, e.g.Article.objects.filter(~Q(id__iexact=self.id))
to exclude the current instance being edited from the list of related_articles a user can see and select from. Creation/setting of the queryset to use could occur within the constructor (__init__
) of a customArticle ModelForm
, or, via some kind of dynamiclimit_choices_to Model
option. This would require a way to grab the instance being edited to use for filtering. - Override the
save_model
function of theArticle Model
orModelAdmin
class to check for and remove itself from therelated_articles
before saving the instance. This still means that admin users can see and select all articles including the instance being edited (for existing articles). - Filter out self references when required for use outside the admin, e.g. templates.
The ideal solution (1) is currently possible to do via custom model forms outside of the admin as it's possible to pass in a filtered queryset variable for the instance being edited to the model form constructor. Question is, can you get at the Article
instance, i.e. 'self' being edited the admin before the form is created to do the same thing.
It could be I am going about this the wrong way, but if your allowed to define a FKF / MTMF to the same model then there should be a way to have the admin - do the right thing - and prevent a user from selecting itself by excluding it in the list of available choices.
Note: Solution 2 and 3 are possible to do now and are provided to try and avoid getting these as answers, ideally i'd like to get an answer to solution 1.