service_object.rb

class ServiceObject
  NULL_LAMBDA = ->(*) { }

  def self.callbacks(*args)
    args.each do |v|
      attr_writer *args.map { |v| "#{v}_callback"}

      define_method("#{v}_callback") do
        instance_variable_get("@#{v}_callback") || NULL_LAMBDA
      end

      define_method(v) do |&callback|
        send("#{v}_callback=", callback)
      end
    end
  end

  def self.call(*args, &block)
    new(*args).tap do |service|
      yield(service) if block_given?
      service.process if service.respond_to?(:process)
    end
  end
end