config_loader.rb

require "ostruct"

module HL7ClientInterface
  
  class Config::FileMissing < Errno::ENOENT; end
  
  def self.config
    @config ||= load_configuration
  end
  
  def self.document_types
    @document_types ||= config['document_types']
  end
  
  def self.load_configuration
    config = YAML::load_file("config.yml") || raise(Config::FileMissing, "Add settings to config.yml")
    settings = config[(ENV["RACK_ENV"] || "development")]
    OpenStruct.new(settings)
  rescue Errno::ENOENT
    raise Config::FileMissing, "config.yml missing"
  end
end

# Now access the config elsewhere using the .config method

HL7ClientFileInterface.config.db_name
HL7ClientFileInterface.config.db_username
# and so forth