Service Layer kind of

ProjectController.rb

class ProjectController < ApplicationController

  def create
    service_layer.save(project)
  end

  private
  def service_layer
    @service_layer ||= ServiceLayer.instance
  end

end

ServiceLayer.rb

class ServiceLayer
  def self.instance
    @service_layer ||= new
  end
end

just include Singleton in the ServiceLayer class and you get the same behavior