Experimental syntax sugar for focused_controller

benefits_controller.rb

require 'focused_controller/controller'

module BitBindery
  BenefitsController = FocusedController::Controller.new do
    common do
      expose(:product)  { @product  ||= shop.product_for_id(params[:product_id]) }
      expose(:benefits) { @benefits ||= product.benefits }
      expose(:benefit)
    end

    action :index do
    end

    action :show do
      def call
        @benefit = benefits.get(params[:id])
      end
    end

    action :new do
      expose(:benefit_setup) { product.new_benefit_setup(params['benefit'], current_user) }

      def call
        render "bit_bindery/benefits/setup/#{benefit_setup.type_id}"
      end
    end

    action :create do
      def call
        @benefit = product.add_benefit(params[:benefit])
        redirect_to(product_benefits_path(product))
      end
    end
  end
end

controller.rb

module FocusedController
  class Controller < Module
    def initialize(base_class = ::ApplicationController)
      @controller_base_class = base_class
      super()
    end

    private

    attr_reader :controller_base_class

    # Define the local Action base class
    def common(&body)
      action_base_class_body_blocks << body
    end

    def action(name, &body)
      class_name = name.to_s.camelize
      action_class = Class.new(action_base_class, &body)
      const_set(class_name, action_class)
    end

    def action_base_class
      body_blocks = action_base_class_body_blocks
      container   = self
      @action_base_class ||= Class.new(controller_base_class) do
        container.const_set :Action, self
        include FocusedController::Mixin
        def run(*args)
          call(*args)
        end
        def call; end
        body_blocks.each do |body|
          module_eval(&body)
        end
      end
    end

    def action_base_class_body_blocks
      (@action_base_class_body_blocks ||= [])
    end
  end
end