Simplified structure after testing in an actual app

lib/draper/base.rb

@@ -101,7 +101,7 @@ module Draper
     #
     # @return [Object] proxy   
     def helpers
-      @helpers ||= ApplicationController.current_view_context
+      Thread.current[:current_view_context]
     end
     alias :h :helpers
 

lib/draper/system.rb

@@ -1,7 +1,7 @@
 module Draper
   class System    
     def self.setup
-      ApplicationController.send(:include, Draper::ViewContext) if defined?(ApplicationController)
+      ActionController::Base.send(:include, Draper::ViewContext) if defined?(ActionController::Base)
     end
   end
 end

lib/draper/view_context.rb

@@ -1,21 +1,10 @@
 module Draper
   module ViewContext
-    module ClassMethods
-      def current_view_context
-        Thread.current[:current_view_context] || 
-          raise("set_current_view_context must be called from a before_filter")
-      end
-    end
-    
-    module InstanceMethods
-      def set_current_view_context
-        Thread.current[:current_view_context] ||= self.class.view_context
-      end
+    def set_current_view_context
+      Thread.current[:current_view_context] ||= self.view_context
     end
     
     def self.included(source)
-      source.send(:include, InstanceMethods)
-      source.send(:extend, ClassMethods)
       source.send(:before_filter, :set_current_view_context)
     end
   end

spec/base_spec.rb

@@ -6,8 +6,10 @@ describe Draper::Base do
   subject{ Draper::Base.new(source) }
   let(:source){ Product.new }
 
-  it "should get a valid view_context" do
-    ApplicationController.current_view_context.should be
+  context(".helpers") do
+    it "should have a valid view_context" do
+      subject.helpers.should be
+    end    
   end
 
   context(".lazy_helpers") do

spec/samples/application_controller.rb

@@ -1,28 +1,32 @@
-class ApplicationController
+module ActionController
+  class Base
+    @@before_filters = []
+    def self.before_filters
+      @@before_filters
+    end
+    def self.before_filter(name)
+      @@before_filters << name
+    end
+  end
+end
+
+class ApplicationController < ActionController::Base
   extend ActionView::Helpers
   extend ActionView::Helpers::TagHelper
   extend ActionView::Helpers::UrlHelper
   extend ApplicationHelper    
   
-  def self.view_context
-    @@view_context ||= ApplicationController
+  def view_context
+    @view_context ||= ApplicationController
   end
   
-  def self.view_context=(input)
-    @@view_context = input
+  def view_context=(input)
+    @view_context = input
   end
   
   def self.hello
     "Hello!"
   end
-  
-  @@before_filters = []
-  def self.before_filters
-    @@before_filters
-  end
-  def self.before_filter(name)
-    @@before_filters << name
-  end
 end
 
 Draper::System.setup

spec/view_context_spec.rb

@@ -10,22 +10,10 @@ describe Draper::ViewContext do
     app_controller.new
   end
   
-  it "implements .current_view_context" do
-    app_controller.should respond_to(:current_view_context)
-  end
-  
   it "implements #set_current_view_context" do
     app_controller_instance.should respond_to(:set_current_view_context)
   end
   
-  it "sets and returns the view context" do
-    fake_context = Object.new
-    Thread.current[:current_view_context] = nil
-    app_controller_instance.class.send(:view_context=, fake_context)
-    app_controller_instance.set_current_view_context
-    app_controller.current_view_context.should === fake_context
-  end
-  
   it "calls #before_filter with #set_current_view_context" do
     app_controller.before_filters.should include(:set_current_view_context)
   end