Rails plugin to store currency rates in the database
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db/migrate
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active_currency.gemspec

README.md

ActiveCurrency

Rails plugin to retrieve and store the currency rates daily to integrate with the money-rails gem.

Rationale

Storing the current currency rates in the database using ActiveCurrency provides the following advantages:

  • Lets you find out what the currency rate you used in your application was at any given time.
  • Does not need to call an API to get the rates when starting or restarting your web server.
  • Choose how often you want to check for a currency (daily for example).
  • Your users do not suffer the cost of making calls to the bank rates API.
  • Your app does not go down when the bank rates API does.
  • When fetching the current rate, it uses your application cache in order not to have to do a database query.

To fetch the rates, it uses the eu_central_bank gem.

Usage

Store the current rate regularly by calling in a scheduled job (using something like sidekiq-scheduler or whenever):

ActiveCurrency::AddRates.new.call

You can then exchange money by using the Money gem:

10.to_money('EUR').exchange_to('USD').cents

Or look up the currency rate:

ActiveCurrency::Rate.value_for('EUR', 'USD', 1.month.ago)
# => 1.151
ActiveCurrency::Rate.where(from: 'EUR', to: 'USD').pluck(:value)
# => [1.162, 1.162, 1.161, 1.161, 1.163, …]

Installation

Add these lines to your application's Gemfile:

# Store and retrieve the currency from the database.
gem 'active_currency'

And in config/initializers/money.rb:

MoneyRails.configure do |config|
  rate_store = ActiveCurrency::RateStore.new(%w[EUR USD])
  config.default_bank = Money::Bank::VariableExchange.new(rate_store)
end

Then call bundle exec rake db:migrate to create the table that holds the currency rates and fill it for the first time.

Tests

In your app test suite you may not want to have to fill your database to be able to exchange currencies.

For that, you can in config/initializers/money.rb:

if Rails.env.test?
  rate_store = ActiveCurrency::MemoryRateStore.new.tap do |store|
    store.add_rate('USD', 'EUR', 0.5)
    store.add_rate('EUR', 'USD', 1.5)
  end
  config.default_bank = Money::Bank::VariableExchange.new(rate_store)
end

Contributing

Please file issues and pull requests on GitHub.

In developemnt, launch specs and code linter by calling:

BUNDLE_GEMFILE=Gemfile-rails3.2 bundle exec rspec && bundle exec rake

License

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