How to use dynamic foreignkey in Django?

Question

I want to connect a single ForeignKey to two different models.

For example:

I have two models named Casts and Articles, and a third model, Faves, for favoriting either of the other models. How can I make the ForeignKey dynamic?

class Articles(models.Model):     title = models.CharField(max_length=100)     body = models.TextField()  class Casts(models.Model):     title = models.CharField(max_length=100)     body = models.TextField()  class Faves(models.Model):     post = models.ForeignKey(**---CASTS-OR-ARTICLES---**)     user = models.ForeignKey(User,unique=True) 

Is this possible?

Answer 1

Here is how I do it:

from django.contrib.contenttypes.models import ContentType from django.contrib.contenttypes import fields   class Photo(models.Model):     picture = models.ImageField(null=True, upload_to='./images/')     caption = models.CharField(_("Optional caption"),max_length=100,null=True, blank=True)      content_type = models.ForeignKey(ContentType)     object_id = models.PositiveIntegerField()     content_object = fields.GenericForeignKey('content_type', 'object_id')  class Article(models.Model):     ....     images     = fields.GenericRelation(Photo) 

You would add something like

    content_type = models.ForeignKey(ContentType)     object_id = models.PositiveIntegerField()     content_object = fields.GenericForeignKey('content_type', 'object_id') 

to Faves and

    fields.GenericRelation(Faves) 

to Article and Cast

contenttypes docs

Answer 2

Here's an approach. (Note that the models are singular, Django automatically pluralizes for you.)

class Article(models.Model):     title = models.CharField(max_length=100)     body = models.TextField()  class Cast(models.Model):     title = models.CharField(max_length=100)     body = models.TextField()  FAVE_CHOICES = (      ('A','Article'),     ('C','Cast'), ) class Fave(models.Model):     type_of_fave = models.CharField( max_length=1, choices=FAVE_CHOICES )     cast = models.ForeignKey(Casts,null=True)     article= models.ForeigKey(Articles,null=True)     user = models.ForeignKey(User,unique=True) 

This rarely presents profound problems. It may require some clever class methods, depending on your use cases.