Do not save class instances, save their names.

Saving instances causes memory leaks in development mode in rails.

lib/paperclip.rb

@@ -318,7 +318,7 @@ module Paperclip
       end
 
       attachment_definitions[name] = {:validations => []}.merge(options)
-      Paperclip.classes_with_attachments << self unless Paperclip.classes_with_attachments.include?(self)
+      Paperclip.classes_with_attachments << self.name unless Paperclip.classes_with_attachments.include?(self.name)
       Paperclip.check_for_url_clash(name,attachment_definitions[name][:url],self.name)
 
       after_save :save_attached_files

lib/paperclip/missing_attachment_styles.rb

@@ -38,7 +38,8 @@ module Paperclip
   #   }
   def self.current_attachments_styles
     Hash.new.tap do |current_styles|
-      Paperclip.classes_with_attachments.each do |klass|
+      Paperclip.classes_with_attachments.each do |klass_name|
+        klass = Paperclip.class_for(klass_name)
         klass.attachment_definitions.each do |attachment_name, attachment_attributes|
           # TODO: is it even possible to take into account Procs?
           next if attachment_attributes[:styles].kind_of?(Proc)

test/paperclip_missing_attachment_styles_test.rb

@@ -15,7 +15,7 @@ class PaperclipMissingAttachmentStylesTest < Test::Unit::TestCase
       assert_kind_of Set, Paperclip.classes_with_attachments 
       assert Paperclip.classes_with_attachments.empty?, 'list should be empty'
       rebuild_model
-      assert_equal [Dummy].to_set, Paperclip.classes_with_attachments
+      assert_equal ['Dummy'].to_set, Paperclip.classes_with_attachments
     end
 
     should "enable to get and set path to registered styles file" do