An example of an extensible responder factory

production_creation_responder.rb

class ProductCreationResponder
  @@responders = []

  def self.build(product)
    responders.detect do |responder|
      responder.applicable_to?(product)
    end.new(product)
  end

  def self.register(responder)
    @@responders << responder
  end

  class FailureResponder
    ProductCreationResponder.register self

    def self.applicable_to?(product)
      product.errors.any?
    end

    def initialize(product)
      @product = product
    end

    def call(responses)
      responses.fetch(response).call(product)
    end

    private

    attr_reader :product

    def response
      :on_failure
    end
  end

  class SuccessResponder
    ProductCreationResponder.register self

    def self.applicable_to?(product)
      product.errors.empty?
    end

    def initialize(product)
      @product = product
    end

    def call(responses)
      responses.fetch(response).call(product)
    end

    private

    attr_reader :product

    def response
      :on_success
    end
  end
end

ProductCreationResponder.build(product).call(
  on_failure: on_failure,
  on_success: on_success,
)