Django FileField generate path based on ForeignKey record's slug field

Question

This is for a game mod filesharing site. I have Apps Mods and Games. Each hold, you guessed it, Mods and Games!

Here is my Mods model:

from django.db import models
# Register storage backend TODO
def mod_directory_path(instance, filename):
    # file will be uploaded to MEDIA_ROOT/<game>/<filename>
    # Example code from https://docs.djangoproject.com/en/1.9/ref/models/fields/
    return 'user_{0}/{1}'.format(instance.user.id, filename)

# Create your models here.
class Mods(models.Model):
    title = models.CharField(max_length=30)
    author = models.CharField(max_length=30)
    game = models.ForeignKey(
        'games.Games',
        on_delete=models.CASCADE,
    )
    website = models.URLField()
    repoWebsite = models.URLField()
    upload = models.FileField(upload_to=mod_directory_path)

Here is my Games model:

from django.db import models

# Create your models here.
class Games(models.Model):
    title = models.CharField(max_length=30)
    developer = models.CharField(max_length=30)
    website = models.URLField()
    slug = models.SlugField()

I want to autoset the mod_directory_path to the slug of the Games model.

For example, if Mod item "Dynamic War Sandbox" has a ForeignKey of a unique ID pointing to the Arma 3 game, I want the file upload path to be based on the slug of the database entry for Arma 3.

MEDIA_ROOT/arma-3/<filename>.

How would I do this?

Answer 1

Something like this should work. The only requirement is that the game already exists in your database before the mod is being created.

def mod_directory_path(instance, filename):
    slug = instance.game.slug
    return os.sep.join([slug, filename])