Set the simple-navigation file path of a Rails Engine app to auto load path of Rails 3 Main App

gistfile1.rb

require "rails"
require 'simple-navigation'

module MyEngine
  class Engine < Rails::Engine

    #Give the absolute path of file
    #config.autoload_paths << File.expand_path("../../../config/navigations", __FILE__)
    SimpleNavigation.config_file_path = File.expand_path("../../../config/navigations", __FILE__)
    
    # We can add all of the public assets from our engine and make them
    # available to use.  This allows us to use javascripts, images, stylesheets
    # etc.
    initializer "static assets" do |app|
      app.middleware.insert_before(::ActionDispatch::Static, ::ActionDispatch::Static, "#{root}/public")
    end
    
   
    #generators for engine models and views
    
    config.app_generators do |g|
      g.orm             :active_record
      g.template_engine :erb
    end
 
  end
end