adv_attr_accessors in ActionMailer are not sent to the views, use the mailer object if you need to access the subject, recipients, from, etc.

actionmailer/lib/action_mailer/adv_attr_accessor.rb

@@ -1,29 +1,25 @@
 module ActionMailer
   module AdvAttrAccessor #:nodoc:
-    def self.included(base)
-      base.extend(ClassMethods)
-    end
+    def adv_attr_accessor(*names)
+      names.each do |name|
+        ivar = "@#{name}"
 
-    module ClassMethods #:nodoc:
-      def adv_attr_accessor(*names)
-        names.each do |name|
-          ivar = "@#{name}"
-
-          define_method("#{name}=") do |value|
-            instance_variable_set(ivar, value)
+        class_eval <<-ACCESSORS, __FILE__, __LINE__ + 1
+          def #{name}=(value)
+            #{ivar} = value
           end
 
-          define_method(name) do |*parameters|
-            raise ArgumentError, "expected 0 or 1 parameters" unless parameters.length <= 1
-            if parameters.empty?
-              if instance_variable_names.include?(ivar)
-                instance_variable_get(ivar)
-              end
+          def #{name}(*args)
+            raise ArgumentError, "expected 0 or 1 parameters" unless args.length <= 1
+            if args.empty?
+              #{ivar} if instance_variable_names.include?(#{ivar.inspect})
             else
-              instance_variable_set(ivar, parameters.first)
+              #{ivar} = args.first
             end
           end
-        end
+        ACCESSORS
+
+        self.protected_instance_variables << ivar if self.respond_to?(:protected_instance_variables)
       end
     end
   end

actionmailer/lib/action_mailer/base.rb

@@ -25,7 +25,8 @@ module ActionMailer #:nodoc:
   #      bcc        ["bcc@example.com", "Order Watcher <watcher@example.com>"]
   #      from       "system@example.com"
   #      subject    "New account information"
-  #      body       :account => recipient
+  #
+  #      @account = recipient
   #    end
   #  end
   #
@@ -45,13 +46,6 @@ module ActionMailer #:nodoc:
   # address. Setting this is useful when you want delivery notifications sent to a different address than
   # the one in <tt>from</tt>.
   #
-  # The <tt>body</tt> method has special behavior. It takes a hash which generates an instance variable
-  # named after each key in the hash containing the value that that key points to.
-  #
-  # So, for example, <tt>body :account => recipient</tt> would result
-  # in an instance variable <tt>@account</tt> with the value of <tt>recipient</tt> being accessible in the
-  # view.
-  #
   #
   # = Mailer views
   #
@@ -71,7 +65,12 @@ module ActionMailer #:nodoc:
   # You can even use Action Pack helpers in these views. For example:
   #
   #   You got a new note!
-  #   <%= truncate(note.body, 25) %>
+  #   <%= truncate(@note.body, 25) %>
+  #
+  # If you need to access the subject, from or the recipients in the view, you can do that through mailer object:
+  #
+  #   You got a new note from <%= mailer.from %>!
+  #   <%= truncate(@note.body, 25) %>
   #
   #
   # = Generating URLs
@@ -254,14 +253,15 @@ module ActionMailer #:nodoc:
   #   and appear last in the mime encoded message. You can also pick a different order from inside a method with
   #   +implicit_parts_order+.
   class Base < AbstractController::Base
-    include AdvAttrAccessor, PartContainer, Quoting, Utils
+    include PartContainer, Quoting, Utils
+    extend  AdvAttrAccessor
 
     include AbstractController::Rendering
     include AbstractController::LocalizedCache
     include AbstractController::Layouts
     include AbstractController::Helpers
 
-    helper ActionMailer::MailHelper
+    helper  ActionMailer::MailHelper
 
     include ActionController::UrlWriter
     include ActionMailer::DeprecatedBody
@@ -289,7 +289,7 @@ module ActionMailer #:nodoc:
     @@default_implicit_parts_order = [ "text/html", "text/enriched", "text/plain" ]
     cattr_accessor :default_implicit_parts_order
 
-    @@protected_instance_variables = []
+    @@protected_instance_variables = %w(@parts @mail)
     cattr_reader :protected_instance_variables
 
     # Specify the BCC addresses for the message

actionmailer/lib/action_mailer/mail_helper.rb

@@ -15,5 +15,10 @@ module ActionMailer
 
       formatted
     end
+
+    # Access the mailer instance.
+    def mailer #:nodoc:
+      @controller
+    end
   end
 end

actionmailer/lib/action_mailer/part.rb

@@ -4,7 +4,8 @@ module ActionMailer
   # and add them to the +parts+ list of the mailer, it is easier
   # to use the helper methods in ActionMailer::PartContainer.
   class Part
-    include AdvAttrAccessor, PartContainer, Utils
+    include PartContainer, Utils
+    extend  AdvAttrAccessor
 
     # Represents the body of the part, as a string. This should not be a
     # Hash (like ActionMailer::Base), but if you want a template to be rendered

actionmailer/test/adv_attr_test.rb

@@ -1,18 +1,36 @@
 require 'abstract_unit'
 require 'action_mailer/adv_attr_accessor'
 
-class AdvAttrTest < Test::Unit::TestCase
+class AdvAttrTest < ActiveSupport::TestCase
   class Person
-    include ActionMailer::AdvAttrAccessor
+    cattr_reader :protected_instance_variables
+    @@protected_instance_variables = []
+
+    extend ActionMailer::AdvAttrAccessor
     adv_attr_accessor :name
   end
 
-  def test_adv_attr
-    bob = Person.new
-    assert_nil bob.name
-    bob.name 'Bob'
-    assert_equal 'Bob', bob.name
+  def setup
+    @person = Person.new
+  end
 
-    assert_raise(ArgumentError) {bob.name 'x', 'y'}
+  def test_adv_attr
+    assert_nil @person.name
+    @person.name 'Bob'
+    assert_equal 'Bob', @person.name
+  end
+
+  def test_adv_attr_writer
+    assert_nil @person.name
+    @person.name = 'Bob'
+    assert_equal 'Bob', @person.name
+  end
+
+  def test_raise_an_error_with_multiple_args
+    assert_raise(ArgumentError) { @person.name('x', 'y') }
+  end
+
+  def test_ivar_is_added_to_protected_instnace_variables
+    assert Person.protected_instance_variables.include?('@name')
   end
 end

actionmailer/test/mail_render_test.rb

@@ -40,13 +40,20 @@ class RenderMailer < ActionMailer::Base
     from       "tester@example.com"
   end
 
-  def included_old_subtemplate(recipient)
+  def mailer_accessor(recipient)
     recipients recipient
-    subject    "Including another template in the one being rendered"
+    subject    "Mailer Accessor"
     from       "tester@example.com"
 
-    @world = "Earth"
-    render :inline => "Hello, <%= render \"subtemplate\" %>"
+    render :inline => "Look, <%= mailer.subject %>!"
+  end
+
+  def no_instance_variable(recipient)
+    recipients recipient
+    subject    "No Instance Variable"
+    from       "tester@example.com"
+
+    render :inline => "Look, subject.nil? is <%= @subject.nil? %>!"
   end
 
   def initialize_defaults(method_name)
@@ -108,6 +115,16 @@ class RenderHelperTest < Test::Unit::TestCase
     mail = RenderMailer.deliver_included_subtemplate(@recipient)
     assert_equal "Hey Ho, let's go!", mail.body.strip
   end
+
+  def test_mailer_accessor
+    mail = RenderMailer.deliver_mailer_accessor(@recipient)
+    assert_equal "Look, Mailer Accessor!", mail.body.strip
+  end
+
+  def test_no_instance_variable
+    mail = RenderMailer.deliver_no_instance_variable(@recipient)
+    assert_equal "Look, subject.nil? is true!", mail.body.strip
+  end
 end
 
 class FirstSecondHelperTest < Test::Unit::TestCase