samnissen / fxer

A simple currency conversion gem based on ECB data

Fxer

Fxer is an exchange rate calculator, using the European Central Bank's rates covering the last 90 days.

Installation

Add this line to your application's Gemfile:

gem 'fxer'

And then execute:

bundle

Or install it yourself as, replacing the version numbers:

gem build fxer.gemspec
gem install fxer-1.2.3.gem

Usage

Simplest exchange

Fxer includes a quick and simple way of obtaining an exchange rate via a separate namespace:

ExchangeRate.at(Date.today, 'EUR', 'AUD')
# => 1.4732

Configurable exchange

For situations where you need more control, the Fxer namespace provides configuration:

exchanger = Fxer::Exchange.new.configure do |config|
  config.permissive = true
  config.source = :ecb
  config.store = "/my/path/"
end

exchanger.convert_at_date(Date.today, 'GBP', 'USD')
# => 1.309507859949982

config.permissive

Fxer by default uses the most recently available data at or before the date indicated. Setting permissive to false changes that, in effect a strict-mode, and an error will be raised if a date doesn't have corresponding data.

config.source

Fxer is designed to accommodate code for additional sources of exchange rate data. Source can only be :ecb as of now.

config.store

The configuration of store allows you to indicate where you have locally stored your exchange data file, so that Fxer does not need to download that data to determine the rate.

Executable exchange

fxer also provides an executable for getting rates in Bash:

FXER_RATE_DATA_PATH="/my/path" fxer "2017-07-18" NOK HKD
# => 0.9689571804652662

where the environment variable for local file hosting is optional.

Data retrieval (also executable)

And fxer will download new ECB data for you, in either Ruby or Bash:

ENV['FXER_RATE_DATA_DIRECTORY'] = "/my/path/"
Fxer::Fetcher::Ecb.download

FXER_RATE_DATA_DIRECTORY="/my/path/" fxer-fetcher ecb

Development

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

Until this is pushed to RubyGems and GitHub, there is no defined development process.

Contributing

Bug reports and pull requests will be welcome once fxer is live at https://github.com/samnissen/fxer.

License

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