Foreigner

A Ruby library to lookup exchange rates based on the ECB feed.

Usage

Importing rates

From the source code directory, you can run the included rake task to get the latest rates from ECB:

rake foreigner:fetch_ecb_rates

Alternatively you can include the rake task in your Rakefile:

require 'foreigner/tasks/rake_task'

This will store the rates as JSON in ./sources/rates.json by default.

Getting exchange rates

Requiring the library:

require 'foreigner'

Fetching rates in Ruby:

Foreigner::Sources::ECB.new.fetch_rates

Getting the exchange rate for a particular date:

Foreigner::ExchangeRate.at(Date.parse("2018-02-20"), :GBP, :USD) # => 0.1399600762181290264e1

The returned value of ExchangeRate.at is a BigDecimal. You can call to_s("f") on it if you want a more human readable representation in the console.

Foreigner::ExchangeRate.at(Date.parse("2018-02-20"), :GBP, :USD).to_s("f") # => "1.399600762181290264"

If there's no exchange rate for the given date the returned value is nil:

Foreigner::ExchangeRate.at(Date.parse("2019-02-20"), :GBP, :USD) # => nil

If there's also no exchange rate for the given currency the returned value is nil:

Foreigner::ExchangeRate.at(Date.parse("2018-02-20"), :GBP, :BTC) # => nil

Configuration

If you want to store the rates file in a different location, you can do the following:

Foreigner.configure do |config|
  config.rates_store = "/tmp/rates.json"
end

Tests

Running the tests:

bundle exec rspec

Possible Improvements

ExchangeRate.at could return a first class ExchangeRate object that encapsulates not just the exchange rate value, but also the currencies that it applies to. However, you would expect this object to behave like a numeric value, so it might be not that straight forward.