Added :relative_root interpolation

lib/paperclip/attachment.rb

@@ -206,6 +206,13 @@ module Paperclip
                           end,
         :attachment    => lambda{|attachment,style| attachment.name.to_s.downcase.pluralize },
         :style         => lambda{|attachment,style| style || attachment.default_style },
+        :relative_root => lambda do |attachment,style| 
+                            if ActionController::AbstractRequest.respond_to?(:relative_url_root)
+                              ActionController::AbstractRequest.relative_url_root
+                            elsif ActionController::Base.respond_to?(:relative_url_root)
+                              ActionController::Base.relative_url_root
+                            end
+                          end
       }
     end
 

test/attachment_test.rb

@@ -106,6 +106,36 @@ class AttachmentTest < Test::Unit::TestCase
     end
   end
 
+  context "An attachment with a :relative_root interpolation" do
+    setup do
+      rebuild_model :url => ":relative_root/:id.png"
+      @dummy = Dummy.new
+      @dummy.stubs(:id).returns(1024)
+      @dummy.avatar = StringIO.new(".")
+
+      ActionController::Base.stubs(:respond_to?).with(:relative_url_root).returns(false)
+      ActionController::Base.stubs(:relative_url_root).returns("/base")
+      ActionController::AbstractRequest.stubs(:respond_to?).with(:relative_url_root).returns(false)
+      ActionController::AbstractRequest.stubs(:relative_url_root).returns("/request")
+    end
+
+    should "return the proper path when the path is nil" do
+      assert_equal "/1024.png", @dummy.avatar.url(:original, false)
+    end
+
+    should "return the proper path when using Rails < 2.1" do
+      ActionController::AbstractRequest.expects(:respond_to?).with(:relative_url_root).returns(true)
+      ActionController::AbstractRequest.expects(:relative_url_root).returns("/request")
+      assert_equal "/request/1024.png", @dummy.avatar.url(:original, false)
+    end
+
+    should "return the proper path when using Rails >= 2.1" do
+      ActionController::Base.expects(:respond_to?).with(:relative_url_root).returns(true)
+      ActionController::Base.expects(:relative_url_root).returns("/base")
+      assert_equal "/base/1024.png", @dummy.avatar.url(:original, false)
+    end
+  end
+
   context "An attachment with :convert_options" do
     setup do
       rebuild_model :styles => {

test/helper.rb

@@ -9,6 +9,7 @@ gem 'sqlite3-ruby'
 
 require 'active_record'
 require 'active_support'
+require 'action_controller'
 begin
   require 'ruby-debug'
 rescue LoadError