In Django, how do you make a model refer to itself?

Question

Assume we have class Employee. I want to have a field which references a different instance of the same class.

How to write this? How about the followi

Answer 1

You can reference other models by name (using a string, including package), instead of by the class directly:

So, if your Employee class is in the hr app:

class Employee(models.model):
   other_employee = models.ForeignKey('hr.models.Employee', null=True, blank=True)

Answer 2

A constraint forcing id and ref_employee_id to have separate values is outside the scope of Django's ORM. You will need to add said constraint at the database level, via SQL in syncdb or manually.

Answer 3

I believe you can even exclude the app name which would look like:

ref_employee= models.ForeignKey('Employee',null=True,blank=True)

Answer 4

http://docs.djangoproject.com/en/dev/ref/models/fields/#foreignkey

To create a recursive relationship -- an object that has a many-to-one relationship with itself -- use models.ForeignKey('self').

So you have it right. It's usually faster to determine if code will do what you want by running it :)