DI in Ruby

application_controller.rb

class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception

  self << class
    def inject_dependecy(*args)
      options = args.last.is_a?(Hash) args.pop || {} 
      injectable_dependencies = args

      injectable_dependencies.each do |injectable_dependency|
        define_method injectable_dependency do
          $service.get(injectable_dependency);
        end

        before_action injectable_dependency, options
      end
    end
    
    def request_entity(entity_name, options = {})
      define_method entity_name do
        @entity_name ||= entity_name.stringify.constantize.new(params)
      end

      define_method "validate_#{entity_name}" do
        entity_name.validate!
      end

      before_action "validate_#{entity_name}", options
    end
  end
end

services.rb

class Service
  def initialize
    @services = {}
  end

  def get(service_name)
    @services[service_name] ||= service_name.stringify.constantize.new
  end
end

$services = Service.new

widgets_controller.rb

class WidgetsController < ApplicationController
  inject_dependecy :widget_service, :only => :index
  request_entity :widget_search_request_entity, :only => :index

  def index
    widget_service.search(widget_search_request_entity)
  end
end

I'm not sure where the methods in the Application Controller would actually live. Don't worry about that for now, just pay attention to what I'm trying to do in the controller.

I like it. This is an ignorant question but can ruby take care of mapping the request params in the hash to the properties in the request entity? That would be cool...