Added post-save and post-delete signals to manage Embed instances. Added the delete...

[philo.git] / contrib / penfield / embed.py

diff --git a/contrib/penfield/embed.py b/contrib/penfield/embed.py
index ea0199f..7f875cc 100644 (file)
--- a/contrib/penfield/embed.py
+++ b/contrib/penfield/embed.py
@@ -42,9 +42,18 @@ class Embed(models.Model):
        embedded = generic.GenericForeignKey("embedded_content_type", "embedded_object_id")
        
        def delete(self):
-               # Unclear whether this would be called by a cascading deletion.
+               # This needs to be called manually.
                super(Embed, self).delete()
-               # Cycle through all the fields in the embedder and remove all references to the embedded object.
+               
+               # Cycle through all the fields in the embedder and remove all references
+               # to the embedded object.
+               embedder = self.embedder
+               for field in embedder._meta.fields:
+                       if isinstance(field, EmbedField):
+                               attr = getattr(embedder, field.attname)
+                               setattr(embedder, field.attname, attr.replace(self.get_embed_tag(), ''))
+               
+               embedder.save()
        
        def get_embed_tag(self):
                """Convenience function to construct the embed tag that would create this instance."""
@@ -55,11 +64,11 @@ class Embed(models.Model):
                app_label = 'penfield'
 
 
-def sync_embedded_objects(model_instance, embedded_instances):
-       # First, fetch all current embeds.
+def sync_embedded_instances(model_instance, embedded_instances):
        model_instance_ct = ContentType.objects.get_for_model(model_instance)
-       current_embeds = Embed.objects.filter()
        
+       # Cycle through all the embedded instances and make sure that they are linked to
+       # the model instance. Track their pks.
        new_embed_pks = []
        for embedded_instance in embedded_instances:
                embedded_instance_ct = ContentType.objects.get_for_model(embedded_instance)
@@ -67,7 +76,7 @@ def sync_embedded_objects(model_instance, embedded_instances):
                new_embed_pks.append(new_embed.pk)
        
        # Then, delete all embed objects related to this model instance which do not relate
-       # to one of the embedded instances.
+       # to one of the newly embedded instances.
        Embed.objects.filter(embedder_content_type=model_instance_ct, embedder_object_id=model_instance.id).exclude(pk__in=new_embed_pks).delete()
 
 
@@ -90,13 +99,30 @@ class EmbedField(TemplateField):
                                elif node.object_pk is not None:
                                        self._embedded_instances.add(node.model.objects.get(pk=node.object_pk))
        
-       #def to_template(self, value):
-       #       return Template("{% load embed %}" + value)
-       
        def pre_save(self, model_instance, add):
                if not hasattr(model_instance, '_embedded_instances'):
                        model_instance._embedded_instances = set()
                model_instance._embedded_instances |= self._embedded_instances
+               return getattr(model_instance, self.attname)
+
+
+# Add a post-save signal function to run the syncer.
+def post_save_embed_sync(sender, instance, **kwargs):
+       if hasattr(instance, '_embedded_instances') and instance._embedded_instances:
+               sync_embedded_instances(instance, instance._embedded_instances)
+models.signals.post_save.connect(post_save_embed_sync)
+
+
+# Deletions can't cascade automatically without a GenericRelation - but there's no good way of
+# knowing what models should have one. Anything can be embedded! Also, cascading would probably
+# bypass the Embed model's delete method.
+def post_delete_cascade(sender, instance, **kwargs):
+       ct = ContentType.objects.get_for_model(sender)
+       embeds = Embed.objects.filter(embedded_content_type=ct, embedded_object_id=instance.id)
+       for embed in embeds:
+               embed.delete()
+       Embed.objects.filter(embedder_content_type=ct, embedder_object_id=instance.id).delete()
+models.signals.post_delete.connect(post_delete_cascade)
 
 
 class Test(models.Model):