Using service layer / service locator pattern with Rails.

gistfile1.rb

class ThingsController < ApplicationController
  def create
    result = service.for(:create_thing).call(current_user, params) # I prefer to pass self
    
    respond_with(result) # then the service can call render, respond_with or a method you write
  end
  
  private
  
  def service
    ServiceLocator.new
  end
end

class ServiceLocator
  def for(name)
    map.fetch(name)
  end
  
  private

  def map
    # This could be loaded from a yaml file or you could infer the class name from the name.
    # Here you are implementing YOUR app's routing independent of delivery (HTTP)
    {
      :create_thing => CreateThing.new(dependencies)
    }
  end

  def dependencies
    # pass in dependencies / configuration
  end
  
end

class CreateThing
  def initialize(dependencies = {})
  end

  # always use a call method unless you have a good reason not to.
  def call(current_user, params)
    # create a thing
  end
end