Получение курса одной валюты на заданную дату от сервиса ЦБ РФ

cbr_rate.rb

# this code is provided under MIT license terms
# real.sergeych@gmail.com

require 'savon'

#
# Интерфейс к сервису по РФ: курс одной валюты на заданную дату
# возвращает #rate как строку, как число можно получить float_rate,
# decimal_rate.
#
# используется сервис: http://www.cbr.ru/DailyInfoWebServ/DailyInfo.asmx?WSDL
#
# @author real.sergeych@gmail.com
class CBRRate
  # @return [String] currency full name as returned by the bank's service
  attr :name,
       # @return [Date] as passed to the constructor
       :date,
       # @return [String] exchange rate as String
       :rate,
       # @return [String] Currency symbolic code, e.g. USD
       :code

  # Creates an instance ot currency rate by loading data from Russia's central bank soap
  # service.
  #
  # @param [Date or Time] date object, time object or anyting that has .strftime() methid
  # @param [String] currency_code known to ЦБ РФ (например EUR)
  def initialize date, currency_code
    # Convert date to something CB interface takes
    cbr_date = date.strftime("%Y-%m-%dT07:00:00+03:00")
    @@client = Savon.client(wsdl: "http://www.cbr.ru/DailyInfoWebServ/DailyInfo.asmx?WSDL", log: false)
    res = @@client.call(:get_curs_on_date, message: {
        'On_date' => cbr_date
    })
    @raw_data = res.body[:get_curs_on_date_response][:get_curs_on_date_result][:diffgram][:valute_data]
    raise ArgumentError, "No rate data returned for #{date}" if @raw_data == nil
    data = @raw_data[:valute_curs_on_date].find{|x| x[:vch_code] == currency_code }
    @rate = data[:vcurs]
    @name = data[:vname].strip
    @code = currency_code
  end

  # rate as float. not recommended. use {#decimal_rate} instead.
  def float_rate
    @float_rate ||= @rate.to_f
  end

  # exhnage rate as a BigDecimal. recommended to use in calculations
  def decimal_rate
    @decimal_rate ||= BigDecimal.new(@rate)
  end

  def to_s
    "#{@name}/Рубль:#{@rate}"
  end
end