pflaenz.li/pflaenzli/pflaenzli/models.py

from django.db import models
from django.dispatch import receiver
from django.contrib.auth.models import AbstractUser
from django.utils import timezone
from django.core.files.storage import default_storage


class PflaenzliUser(AbstractUser):
    email = models.EmailField(max_length=254)
    zipcode = models.PositiveIntegerField(blank=True, null=True)


class Offer(models.Model):
    created = models.DateTimeField(default=timezone.now)
    user = models.ForeignKey(PflaenzliUser, on_delete=models.CASCADE)
    title = models.CharField(max_length=50)
    description = models.TextField(max_length=5000)
    zipcode = models.IntegerField(blank=True, default=0)
    image = models.ImageField(upload_to="uploads/")


class Wish(models.Model):
    created = models.DateTimeField(default=timezone.now)
    user = models.ForeignKey(PflaenzliUser, on_delete=models.CASCADE)
    title = models.CharField(max_length=200)


@receiver(models.signals.post_delete, sender=Offer)
def auto_delete_image_on_delete(sender, instance, **kwargs):
    """
    Deletes image from filesystem when corresponding `Offer` object is deleted.
    """
    if instance.image and os.path.isfile(instance.image.path):
        default_storage.delete(instance.image.path)


@receiver(models.signals.pre_save, sender=Offer)
def delete_old_image(sender, instance, **kwargs):
    try:
        old_image = sender.objects.get(pk=instance.pk).image
    except sender.DoesNotExist:
        return False

    default_storage.delete(old_image.path)