Include a module other than top-level Paperclip to prevent namespace collisions.

lib/paperclip.rb

@@ -103,15 +103,6 @@ module Paperclip
       CommandLine.new(cmd, *params).run
     end
 
-    def included base #:nodoc:
-      base.extend ClassMethods
-      if base.respond_to?("set_callback")
-        base.send :include, Paperclip::CallbackCompatability::Rails3
-      else
-        base.send :include, Paperclip::CallbackCompatability::Rails21
-      end
-    end
-
     def processor name #:nodoc:
       name = name.to_s.camelize
       processor = Paperclip.const_get(name)
@@ -159,6 +150,17 @@ module Paperclip
   class InfiniteInterpolationError < PaperclipError #:nodoc:
   end
 
+  module Glue
+    def self.included base #:nodoc:
+      base.extend ClassMethods
+      if base.respond_to?("set_callback")
+        base.send :include, Paperclip::CallbackCompatability::Rails3
+      else
+        base.send :include, Paperclip::CallbackCompatability::Rails21
+      end
+    end
+  end
+
   module ClassMethods
     # +has_attached_file+ gives the class it is called on an attribute that maps to a file. This
     # is typically a file stored somewhere on the filesystem and has been uploaded by a user.

lib/paperclip/railtie.rb

@@ -17,7 +17,7 @@ module Paperclip
 
   class Railtie
     def self.insert
-      ActiveRecord::Base.send(:include, Paperclip)
+      ActiveRecord::Base.send(:include, Paperclip::Glue)
       File.send(:include, Paperclip::Upfile)
     end
   end

test/helper.rb

@@ -61,10 +61,10 @@ ActiveRecord::Base.logger = ActiveSupport::BufferedLogger.new(File.dirname(__FIL
 ActiveRecord::Base.establish_connection(config['test'])
 
 def reset_class class_name
-  ActiveRecord::Base.send(:include, Paperclip)
+  ActiveRecord::Base.send(:include, Paperclip::Glue)
   Object.send(:remove_const, class_name) rescue nil
   klass = Object.const_set(class_name, Class.new(ActiveRecord::Base))
-  klass.class_eval{ include Paperclip }
+  klass.class_eval{ include Paperclip::Glue }
   klass
 end
 
@@ -90,11 +90,11 @@ def rebuild_model options = {}
 end
 
 def rebuild_class options = {}
-  ActiveRecord::Base.send(:include, Paperclip)
+  ActiveRecord::Base.send(:include, Paperclip::Glue)
   Object.send(:remove_const, "Dummy") rescue nil
   Object.const_set("Dummy", Class.new(ActiveRecord::Base))
   Dummy.class_eval do
-    include Paperclip
+    include Paperclip::Glue
     has_attached_file :avatar, options
   end
 end

test/paperclip_test.rb

@@ -172,6 +172,12 @@ class PaperclipTest < Test::Unit::TestCase
       end
     end
 
+    should "not have Attachment in the ActiveRecord::Base namespace" do
+      assert_raises(NameError) do
+        ActiveRecord::Base::Attachment
+      end
+    end
+
     def self.should_validate validation, options, valid_file, invalid_file
       context "with #{validation} validation and #{options.inspect} options" do
         setup do