Delete photo when not referenced any more by Recette instance

recette/models.py

@@ -1,4 +1,6 @@
+import os
 from django.db import models
+from django.dispatch import receiver
 from django.urls import reverse
 
 from .fields import ChoiceArrayField
@@ -52,3 +54,35 @@ class Composition(models.Model):
 
     def __str__(self):
         return "%s %s %s" % (self.quantite, self.unite.nom, self.ingredient.nom)
+
+
+@receiver(models.signals.post_delete, sender=Recette)
+def auto_delete_photo_on_delete(sender, instance, **kwargs):
+    """
+    Delete file from filesystem
+    when corresponding `Recette` object is deleted.
+    """
+    if instance.photo:
+        if os.path.isfile(instance.photo.path):
+            os.remove(instance.photo.path)
+
+
+@receiver(models.signals.pre_save, sender=Recette)
+def auto_delete_photo_on_change(sender, instance, **kwargs):
+    """
+    Delete old file from filesystem
+    when corresponding `Recette` object is updated
+    with new file.
+    """
+    if not instance.pk:
+        return False
+
+    try:
+        old_file = Recette.objects.get(pk=instance.pk).photo
+    except Recette.DoesNotExist:
+        return False
+
+    new_file = instance.photo
+    if not old_file == new_file:
+        if os.path.isfile(old_file.path):
+            os.remove(old_file.path)