Reduce class-oriented programming to help metaclasses

lib/paperclip/instance_methods.rb

@@ -2,11 +2,11 @@ module Paperclip
   module InstanceMethods #:nodoc:
     def attachment_for name
       @_paperclip_attachments ||= {}
-      @_paperclip_attachments[name] ||= Attachment.new(name, self, self.class.attachment_definitions[name])
+      @_paperclip_attachments[name] ||= Attachment.new(name, self, attachment_definitions[name])
     end
 
     def each_attachment
-      self.class.attachment_definitions.each do |name, definition|
+      self.attachment_definitions.each do |name, definition|
         yield(name, attachment_for(name))
       end
     end

test/helper.rb

@@ -103,6 +103,13 @@ def rebuild_class options = {}
   end
 end
 
+def rebuild_meta_class_of obj, options = {}
+  (class << obj; self; end).tap do |metaklass|
+    metaklass.has_attached_file :avatar, options
+    Paperclip.reset_duplicate_clash_check!
+  end
+end
+
 class FakeModel
   attr_accessor :avatar_file_name,
                 :avatar_file_size,

test/meta_class_test.rb

+require './test/helper'
+
+class MetaClassTest < Test::Unit::TestCase
+  context "A meta-class of dummy" do
+    setup do
+      rebuild_model
+      @file = File.new(fixture_file("5k.png"), 'rb')
+    end
+
+    teardown { @file.close }
+
+    should "be able to use Paperclip like a normal class" do
+      reset_class("Dummy")
+      @dummy = Dummy.new
+
+      assert_nothing_raised do
+        rebuild_meta_class_of(@dummy)
+      end
+    end    
+
+    should "work like any other instance" do
+      reset_class("Dummy")
+      @dummy = Dummy.new
+      rebuild_meta_class_of(@dummy)
+
+      assert_nothing_raised do
+        @dummy.avatar = @file
+      end
+      assert @dummy.save
+    end
+  end
+end
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