From 4f28c4fc9a51bbab76d5dcde033c47aa6711339b Mon Sep 17 00:00:00 2001
From: "Justin S. Leitgeb" <justin@stackbuilders.com>
Date: Sat, 10 Mar 2012 15:37:04 -0500
Subject: [PATCH] Add ability to define callbacks in ActionMailer using
 AbstractController::Callbacks.

Prior to this commit, there isn't a good way of adding things like
default inline attachments to an email.  This Stack Overflow thread
shows people using hooks like the 'default' method in ActionMailer::Base
to call a Proc for message configuration:

http://stackoverflow.com/questions/5113121/rails-use-same-attachment-for-all-emails-using-layout

This has the unintended side effect of setting a message header, so it's not a good solution.

This pull request adds support for message modifications by including AbstractController:Callbacks
in ActionMailer::Base. It includes tests and documentation for the functionality
provided by including this module.
---
 actionmailer/lib/action_mailer/base.rb | 28 ++++++++++++++++
 actionmailer/test/base_test.rb         | 46 ++++++++++++++++++++++++++
 2 files changed, 74 insertions(+)

diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index 1800ff5839..64f82f24a2 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -267,6 +267,33 @@ module ActionMailer #:nodoc:
   # set something in the defaults using a proc, and then set the same thing inside of your
   # mailer method, it will get over written by the mailer method.
   #
+  # = Callbacks
+  #
+  # You can specify callbacks using before_filter and after_filter for configuring your messages.
+  # This may be useful, for example, when you want to add default inline attachments for all
+  # messages sent out by a certain mailer class:
+  #
+  #   class Notifier < ActionMailer::Base
+  #     before_filter :add_inline_attachment!
+  #
+  #     def welcome
+  #       mail
+  #     end
+  #
+  #     private
+  #
+  #       def add_inline_attachment!
+  #         attachments.inline["footer.jpg"] = File.read('/path/to/filename.jpg')
+  #       end
+  #   end
+  #
+  # Callbacks in ActionMailer are implemented using AbstractController::Callbacks, so you
+  # can define and configure callbacks in the same manner that you would use callbacks in
+  # classes that inherit from ActionController::Base.
+  #
+  # Note that unless you have a specific reason to do so, you should prefer using before_filter
+  # rather than after_filter in your ActionMailer classes so that headers are parsed properly.
+  #
   # = Configuration options
   #
   # These options are specified on the class level, like
@@ -330,6 +357,7 @@ class Base < AbstractController::Base
     include AbstractController::Helpers
     include AbstractController::Translation
     include AbstractController::AssetPaths
+    include AbstractController::Callbacks
 
     self.protected_instance_variables = [:@_action_has_layout]
 
diff --git a/actionmailer/test/base_test.rb b/actionmailer/test/base_test.rb
index 8d60e028cb..aed3ee1874 100644
--- a/actionmailer/test/base_test.rb
+++ b/actionmailer/test/base_test.rb
@@ -552,6 +552,52 @@ def self.delivering_email(mail)
     assert_equal("Thanks for signing up this afternoon", mail.subject)
   end
 
+  test "modifying the mail message with a before_filter" do
+    class BeforeFilterMailer < ActionMailer::Base
+      before_filter :add_special_header!
+
+      def welcome ; mail ; end
+
+      private
+      def add_special_header!
+        headers('X-Special-Header' => 'Wow, so special')
+      end
+    end
+
+    assert_equal('Wow, so special', BeforeFilterMailer.welcome['X-Special-Header'].to_s)
+  end
+
+  test "modifying the mail message with an after_filter" do
+    class AfterFilterMailer < ActionMailer::Base
+      after_filter :add_special_header!
+
+      def welcome ; mail ; end
+
+      private
+      def add_special_header!
+        headers('X-Special-Header' => 'Testing')
+      end
+    end
+
+    assert_equal('Testing', AfterFilterMailer.welcome['X-Special-Header'].to_s)
+  end
+
+  test "adding an inline attachment using a before_filter" do
+    class DefaultInlineAttachmentMailer < ActionMailer::Base
+      before_filter :add_inline_attachment!
+
+      def welcome ; mail ; end
+
+      private
+      def add_inline_attachment!
+        attachments.inline["footer.jpg"] = 'hey there'
+      end
+    end
+
+    mail = DefaultInlineAttachmentMailer.welcome
+    assert_equal('image/jpeg; filename=footer.jpg', mail.attachments.inline.first['Content-Type'].to_s)
+  end
+
   test "action methods should be refreshed after defining new method" do
     class FooMailer < ActionMailer::Base
       # this triggers action_methods