Django: Add foreign key in same model but different class

Question

I'm new to Django. How to add foreign key in same Model of different class?

from django.db import models

class Student(models.Model):
    name = models.CharField(max_length=20)
    address = models.CharField(max_length=200)

class Player(models.Model):
    student = models.ForeignKey(
        self.Student, #?
        on_delete = models.CASCADE,
    )
    sports_name = models.CharField(max_length=20)

neverwalkaloner · Accepted Answer · 2018-03-26T06:17:22.837

You don't need use self, just leave only class name Student:

class Player(models.Model):
    student = models.ForeignKey(
        Student,
        on_delete = models.CASCADE,
    )
    sports_name = models.CharField(max_length=20)

Use self in case you need to get attribute of current instance: self.some_attribute, check this question for more details.

Also you can pass model name as the string:

class Player(models.Model):
    student = models.ForeignKey(
        'Student',
        on_delete = models.CASCADE,
    )
    sports_name = models.CharField(max_length=20)

It's called lazy relationship and usefull when related model is not defined yet.

OK. this should work. I thought I have to use Django's Generic Relations — waghso, Mar 26 '18 at 06:34

score 0 · Answer 2 · answered Mar 26 '18 at 07:33

You don't actually need to use self.Student.Use this

class Student(models.Model):
    name = models.CharField(max_length=20)
    address = models.CharField(max_length=200)

class Player(models.Model):
    student = models.ForeignKey(self.Student, on_delete=models.CASCADE, null=True, blank=True)
    sports_name = models.CharField(max_length=20)

Don't forget to use

python manage.py makemigrations and python manage.py migrate

after you had done changes in model.

In some point -in-time you might want to use same model to have ForeignKey field. For that you may use self or the current model you want to make it as a Foreign Key('self' or 'Player') as string

class Student(models.Model):
    name = models.ForeignKey(models.CharField(max_length=20))
    address = models.CharField(max_length=20)
    related_student = models.ForeignKey(Student, on_delete = models.CASCADE, null=True, blank=True)

For this Example you may refer. Can I Make a foreignKey to same model in django?

Django: Add foreign key in same model but different class

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