How would I create a Django model called Category that can relate to itself (to create sub-categories)

Question

I want to create a Category class that may or may not have a subcategory or it may or may not itself be a subclass of another Category object.

This doesn't work, but it gives an idea of what I'm trying to do:

class Category(models.Model):  
    about = models.TextField(blank=True)
    parent_cat = models.ForeignKey(Category, blank=False, null=True)
    slug = models.SlugField(unique=True, help_text = SLUG_HELP)    
    title = models.CharField(max_length = 26, unique=True)

...

What works right now is I have a SubCategory class that can relate to a Category. However I would like to make the code more flexible by just allow Categories to be sub-categories of themselves. Then I can have an unlimited number of parents/children. Can someone suggest how I might be able to do this?

Answer 1

Your reference to subclassing and inheritance is confusing. You've got a standard recursive relationship, which works fine via a ForeignKey. The only thing you'd need to do would be to define the FK as described in the documentation:

parent_cat = models.ForeignKey('self', blank=False, null=True)

What else "doesn't work" about the code you have posted?

Answer 2

You can use my model as an example. I use django-mptt to render a tree-listing view on the front end.

Including foreign key count in django mptt full tree listing?

class Category ( models.Model ):
    name = models.CharField( max_length=100 )
    parent = models.ForeignKey('self', null=True, blank=True, related_name='children')
    slug = models.SlugField(unique=True)

mptt.register(Category)