Access module Configuration constant from another class - ruby

Question

I am trying to understand how the following code is able to do this:
attr_accessor *Configuration::VALID_CONFIG_KEYS
Without requiring the Configuration file. Here is part of the code:
require 'openamplify/analysis/context'
require 'openamplify/connection'
require 'openamplify/request'
module OpenAmplify
# Provides access to the OpenAmplify API http://portaltnx20.openamplify.com/AmplifyWeb_v20/
#
# Basic usage of the library is to call supported methods via the Client class.
#
# text = "After getting the MX1000 laser mouse and the Z-5500 speakers i fell in love with logitech"
# OpenAmplify::Client.new.amplify(text)
class Client
include OpenAmplify::Connection
include OpenAmplify::Request
attr_accessor *Configuration::VALID_CONFIG_KEYS
def initialize(options={})
merged_options = OpenAmplify.options.merge(options)
Configuration::VALID_CONFIG_KEYS.each do |key|
send("#{key}=", merged_options[key])
end
end
....
end
And this is the Configuration module:
require 'openamplify/version'
# TODO: output_format, analysis, scoring can be specied in the client and becomes the default unless overriden
module OpenAmplify
# Defines constants and methods for configuring a client
module Configuration
VALID_CONNECTION_KEYS = [:endpoint, :user_agent, :method, :adapter].freeze
VALID_OPTIONS_KEYS = [:api_key, :analysis, :output_format, :scoring].freeze
VALID_CONFIG_KEYS = VALID_CONNECTION_KEYS + VALID_OPTIONS_KEYS
DEFAULT_ENDPOINT = 'http://portaltnx20.openamplify.com/AmplifyWeb_v21/AmplifyThis'
DEFAULT_HTTP_METHOD = :get
DEFAULT_HTTP_ADAPTER = :net_http
DEFAULT_USER_AGENT = "OpenAmplify Ruby Gem #{OpenAmplify::VERSION}".freeze
DEFAULT_API_KEY = nil
DEFAULT_ANALYSIS = :all
DEFAULT_OUTPUT_FORMAT = :xml
DEFAULT_SCORING = :standard
DEFAULT_SOURCE_URL = nil
DEFAULT_INPUT_TEXT = nil
attr_accessor *VALID_CONFIG_KEYS
....
end
This is from this repository: OpenAmplify

Answer 1

First of all, in both configuration.rb and client.rb, they're using the same naming space, which is module OpenAmplify.
Even though configuration.rb is not required in client.rb, the convention of Ruby project usually requires all necessary files in one file (normally the same name as the name space, and placed in {ProjectName}/lib/, in this case the file is openamplify/lib/openamplify.rb).
So if you go to openamplify/lib/openamplify.rb, you'll notice it actually requires all those two files:
require 'openamplify/configuration'
require 'openamplify/client'
And since constants are already defined in configuration.rb:
module OpenAmplify
module Configuration
VALID_CONFIG_KEYS = ...
end
end
Then obviously constant VALID_CONFIG_KEYS is visible in the same module (re-opened by client.rb) by Configuration::VALID_CONFIG_KEYS (and the * in front just means exploding array, because VALID_CONFIG_KEYS is an array of symbols)
module OpenAmplify
class Client
attr_accessor *Configuration::VALID_CONFIG_KEYS
end
end