A list of ImageSpec names are now stored on the model.

Previously, ImageSpecFile instances were retrieved (for saving and deleting,
among other possibilities) by iterating over the model instance's attributes.
This change adds ImageSpecFile names to a list (spec_file_names) on an
imagekit meta object on the model (_ik), making later retrieval much cheaper
and more straightforward.

imagekit/models.py

@@ -77,6 +77,13 @@ class ImageSpec(_ImageSpecMixin):
 
     def contribute_to_class(self, cls, name):
         setattr(cls, name, _ImageSpecDescriptor(self, name))
+        try:
+            ik = getattr(cls, '_ik')
+        except AttributeError:
+            ik = type('ImageKitMeta', (object,), {'spec_file_names': []})
+            setattr(cls, '_ik', ik)
+        ik.spec_file_names.append(name)
+
         # Connect to the signals only once for this class.
         uid = '%s.%s' % (cls.__module__, cls.__name__)
         post_save.connect(_post_save_handler,

imagekit/utils.py

@@ -13,16 +13,12 @@ def img_to_fobj(img, format, **kwargs):
 
 
 def get_spec_files(instance):
-    from imagekit.models import ImageSpecFile
-    spec_files = []
-    for key in dir(instance):
-        try:
-            value = getattr(instance, key)
-        except AttributeError:
-            continue
-        if isinstance(value, ImageSpecFile):
-            spec_files.append(value)
-    return spec_files
+    try:
+        ik = getattr(instance, '_ik')
+    except AttributeError:
+        return []
+    else:
+        return [getattr(instance, n) for n in ik.spec_file_names]
 
 
 def open_image(target):