Fix borrowable autocompletion

media/models.py

@@ -44,7 +44,17 @@ class Borrowable(PolymorphicModel):
     )
 
     def __str__(self):
-        return self.title
+        obj = self
+        if obj.__class__ == Borrowable:
+            # Get true object instance, useful for autocompletion
+            obj = Borrowable.objects.get(pk=obj.pk)
+
+        title = obj.title
+        if hasattr(obj, 'subtitle'):
+            subtitle = obj.subtitle
+            if subtitle:
+                title = f"{title} : {subtitle}"
+        return title
 
     class Meta:
         verbose_name = _('borrowable')
@@ -99,12 +109,6 @@ class Book(Medium):
         null=True,
     )
 
-    def __str__(self):
-        if self.subtitle:
-            return "{} : {}".format(self.title, self.subtitle)
-        else:
-            return self.title
-
     class Meta:
         verbose_name = _("book")
         verbose_name_plural = _("books")