Get a YAML dictionary of ISO 4217 and ISO 3166-1 mapping / Country-currency binding - Made for the `exchange` gem

get_country_currency.rb

require "json"
require "net/http"
require "uri"
require 'yaml'

uri = URI.parse("http://restcountries.eu/rest/v1/all")
http = Net::HTTP.new(uri.host, uri.port)
request = Net::HTTP::Get.new(uri.request_uri)
response = http.request(request)
 
if response.code == "200"
  result = JSON.parse(response.body)
  dict = Hash.new
  result.each do |country|
    ## If a country has more than one currency, we have to check 
    ## on the ISO norm which one is the actually used currency. The 'puts' line displays those countries that need double-checking.
    if country["currencies"].length > 1
      puts "#{country["name"]} (#{country["alpha2Code"]}-#{country["alpha3Code"]}): #{country["currencies"].length}"
    end
    currency = country["currencies"][0].downcase.to_sym
    dict[country["alpha2Code"]] = currency
    dict[country["alpha3Code"]] = currency
  end
  File.open('iso4217_country_map.yml','w') do |s|
    s.puts dict.to_yaml
  end
end