initialize_template_class

# File actionpack/lib/action_controller/base.rb, line 1117
      def initialize_template_class(response)
        unless @@template_class
          raise "You must assign a template class through ActionController.template_class= before processing a request"
        end

        response.template = ActionView::Base.new(view_paths, {}, self)
        response.template.extend self.class.master_helper_module
        response.redirected_to = nil
        @performed_render = @performed_redirect = false
      end