Helper support for ActionMailer

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1446 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

1 files changed, 136 insertions, 0 deletions

diff --git a/actionmailer/lib/action_mailer/helpers.rb b/actionmailer/lib/action_mailer/helpers.rb
new file mode 100644
index 0000000000..c0e02edfb1
--- /dev/null
+++ b/actionmailer/lib/action_mailer/helpers.rb
@@ -0,0 +1,136 @@
+module ActionMailer #:nodoc:
+  module Helpers #:nodoc:
+    def self.append_features(base)
+      super
+
+      # Initialize the base module to aggregate its helpers.
+      base.class_inheritable_accessor :master_helper_module
+      base.master_helper_module = Module.new
+
+      # Extend base with class methods to declare helpers.
+      base.extend(ClassMethods)
+
+      base.class_eval do
+        # Wrap inherited to create a new master helper module for subclasses.
+        class << self
+          alias_method :inherited_without_helper, :inherited
+          alias_method :inherited, :inherited_with_helper
+        end
+
+        # Wrap initialize_template_class to extend new template class
+        # instances with the master helper module.
+        alias_method :initialize_template_class_without_helper, :initialize_template_class
+        alias_method :initialize_template_class, :initialize_template_class_with_helper
+      end
+    end
+
+    # The template helpers serves to relieve the templates from including the same inline code again and again. It's a
+    # set of standardized methods for working with forms (FormHelper), dates (DateHelper), texts (TextHelper), and 
+    # Active Records (ActiveRecordHelper) that's available to all templates by default.
+    #
+    # It's also really easy to make your own helpers and it's much encouraged to keep the template files free
+    # from complicated logic. It's even encouraged to bundle common compositions of methods from other helpers 
+    # (often the common helpers) as they're used by the specific application.
+    # 
+    #   module MyHelper
+    #     def hello_world() "hello world" end
+    #   end
+    # 
+    # MyHelper can now be included in a controller, like this:
+    # 
+    #   class MyController < ActionController::Base
+    #     helper :my_helper
+    #   end
+    # 
+    # ...and, same as above, used in any template rendered from MyController, like this:
+    # 
+    # Let's hear what the helper has to say: <tt><%= hello_world %></tt>
+    module ClassMethods
+      # Makes all the (instance) methods in the helper module available to templates rendered through this controller.
+      # See ActionView::Helpers (link:classes/ActionView/Helpers.html) for more about making your own helper modules 
+      # available to the templates.
+      def add_template_helper(helper_module) #:nodoc:
+        master_helper_module.module_eval "include #{helper_module}"
+      end
+
+      # Declare a helper:
+      #   helper :foo
+      # requires 'foo_helper' and includes FooHelper in the template class.
+      #   helper FooHelper
+      # includes FooHelper in the template class.
+      #   helper { def foo() "#{bar} is the very best" end }
+      # evaluates the block in the template class, adding method #foo.
+      #   helper(:three, BlindHelper) { def mice() 'mice' end }
+      # does all three.
+      def helper(*args, &block)
+        args.flatten.each do |arg|
+          case arg
+            when Module
+              add_template_helper(arg)
+            when String, Symbol
+              file_name  = arg.to_s.underscore + '_helper'
+              class_name = file_name.camelize
+                
+              begin
+                require_dependency(file_name)
+              rescue LoadError => load_error
+                requiree = / -- (.*?)(\.rb)?$/.match(load_error).to_a[1]
+                msg = (requiree == file_name) ? "Missing helper file helpers/#{file_name}.rb" : "Can't load file: #{requiree}"
+                raise LoadError.new(msg).copy_blame!(load_error)
+              end
+
+              add_template_helper(class_name.constantize)
+            else
+              raise ArgumentError, 'helper expects String, Symbol, or Module argument'
+          end
+        end
+
+        # Evaluate block in template class if given.
+        master_helper_module.module_eval(&block) if block_given?
+      end
+
+      # Declare a controller method as a helper.  For example,
+      #   helper_method :link_to
+      #   def link_to(name, options) ... end
+      # makes the link_to controller method available in the view.
+      def helper_method(*methods)
+        methods.flatten.each do |method|
+          master_helper_module.module_eval <<-end_eval
+            def #{method}(*args, &block)
+              controller.send(%(#{method}), *args, &block)
+            end
+          end_eval
+        end
+      end
+
+      # Declare a controller attribute as a helper.  For example,
+      #   helper_attr :name
+      #   attr_accessor :name
+      # makes the name and name= controller methods available in the view.
+      # The is a convenience wrapper for helper_method.
+      def helper_attr(*attrs)
+        attrs.flatten.each { |attr| helper_method(attr, "#{attr}=") }
+      end
+
+      private 
+        def inherited_with_helper(child)
+          inherited_without_helper(child)
+          begin
+            child.master_helper_module = Module.new
+            child.master_helper_module.send :include, master_helper_module
+            child.helper child.name.underscore
+          rescue MissingSourceFile => e
+            raise unless e.is_missing?("helpers/#{child.name.underscore}_helper")
+          end
+        end        
+    end
+
+    private
+      # Extend the template class instance with our controller's helper module.
+      def initialize_template_class_with_helper(assigns)
+        returning(template = initialize_template_class_without_helper(assigns)) do
+          template.extend self.class.master_helper_module
+        end
+      end
+  end
+end