Make URLs more visible in HTTP-based gateways. In HTTP-based gateways, URL visibility is an important feature because it gives the reader a very good idea of the overall functionality of the class. This proposal strives to achieve that goal and was instigated by @tjsousa, who brought the problem up while reviewing some code.

configurable_gateway.rb

# simple DSL to describe and build URLs in an HTTP gateway

module ConfigurableGateway

  def self.included(base)
    base.extend(ClassMethods)
  end

  def url_for(name, params = nil)
    # probably should be replaced by an automatic forwarding mechanism
    self.class.instance_variable_get("@gateway_config").url_for(name, params)
  end

  module ClassMethods

    def configuration(&block)
      @gateway_config ||= GatewayConfiguration.new
      @gateway_config.instance_eval(&block)
    end

    private

    class GatewayConfiguration

      def url_for(name, params = {})
        url = instance_variable_get("@#{name}_url")
        replace_params(url, params)
      end

      private

      def replace_params(url, params)
        params.each do |name, value|
          url.gsub!(":#{name}", value.to_s)
        end
        url
      end

      def method_missing(method, *args)
        url = args.first
        instance_variable_set("@#{method}", url)
      end

    end

  end

end

class HTTPGateway

  include ConfigurableGateway

  configuration do
    user_url 'http://example.com/users/:user_id'
    user_message_url 'http://example.com/users/:user_id/messages/:message_id'
  end

end

# Client code demo

gateway = HTTPGateway.new
puts gateway.url_for(:user, {user_id: 123})
puts gateway.url_for(:user_message, {user_id: 123, message_id: 321})

me likes it!

Looks pretty interesting! It reminded me a bit of HTTParty except that here it's generating URLs as opposed to actual HTTP requests.

The only thing is that it goes against hypermedia principles, but some APIs I guess just don't work that way and are completely URL based, and an approach like this might be handy :)