Concurrency is a lightweight gem that can be deployed for foreign exchange and currency conversion operation complying the latest rates provided by https://free.currencyconverterapi.com/
It should be noted that the rates provided by the parent API are refreshed every 30 minutes and are not in real time.

This gem can implement the currency conversion operation for the following national currencies -

"AUD" - Australian Dollar, "BGN" - Bulgarian Lev, "BRL" - Brazilian Real, "CAD" - Canadian Dollar, "CHF" - Swiss Franc, "CNY" - Chinese Yuan, "CZK" - Czech Koruna, "DKK" - Danish Krone , "GBP" - British Pound, "HKD" - Hong Kong Dollar, "HRK" - Croatian Kuna, "HUF" - Hungarian Forint, "IDR" - Indonesian Rupiah, "ILS" - Israeli New Shekel, "INR" - Indian Rupee, "JPY" - Japanese Yen, "KRW" - South Korean Won, "MXN" - Mexican Peso, "MYR" - Malaysian Ringgit, "NOK" - Norwegian Krone, "NZD" - New Zealand Dollar, "PHP" - Philippine Peso, "PLN" - Polish Zloty, "RON" - Romanian Leu, "RUB" - Russian Ruble, "SEK" - Swedish Krona, "SGD" - Singapore Dollar, "THB" - Thai Baht, "TRY" - Turkish Lira, "USD" - United States Dollar, "ZAR" - South African Rand,

This gem requires JSON. If you're using JRuby < 1.7.0 you'll need to add gem "json" to your Gemfile or similar.

To install Concurrency on the default Rails stack, just put this line in your Gemfile:

    gem 'concurrency'

And then execute:

$ bundle

Or install it yourself as:

$ gem install concurrency

    Concurrency.convert(AMOUNT_TO_BE_CONVERTED, CONVERT_FROM_CURRENCY, CONVERT_TO_CURRENCY)

    Concurrency.convert(100, "NZD", "INR")      # would convert 100 New Zealand Dollars to Indian Rupees

    <%= Concurrency.convert(100, "NZD", "INR") %>      

    Concurrency.conversion_rate("NZD", "INR")    # will return the value of 1 New Zealand Dollar in Indian Rupees

In order to establish default conversion currencies, paste the following code in .../config/initializers/concurrency.rb

    Concurrency.configure do |config|
        config.from_currency = "USD"    #Default value
        config.to_currency = "INR"      #Default value
        config.api_key = ENV['CONCURRENCY_APIKEY']   #Mandatory value
    end

    Concurrency.convert(100)    # would convert 100 USD to INR
    Concurrency.convert(100, "NZD")     # would convert 100 USD to NZD
    Concurrency.conversion_rate     # would convert 1 USD to INR

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Get your API Key here https://free.currencyconverterapi.com/ API Key is mandatory to get the converstion rates.

Bug reports and pull requests are welcome on GitHub at https://github.com/naman2202/concurrency. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the Concurrency project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.