ActiveCurrency

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

Storing the current currency rates with ActiveCurrency provides the following advantages:

• Lets you query for the currency rate you actually used in your application at any given time.
• Does not need to call an API to get the rates when starting or restarting your web server.
• Does not depend on the file system to store cached rates.
• Choose how often you want to update the currency rates (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.

To fetch the current rate it uses your application cache instead of making a call to the database.

Store the current rate regularly by calling in a scheduled job (using something like sidekiq-scheduler, whenever, or active_scheduler) with the currencies you want to store:

ActiveCurrency::AddRates.call(currencies: %w[EUR USD])

You can then exchange money by using the Money gem helpers:

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

If you need to look up the previous currency rates:

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, …]

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|
  config.default_bank = ActiveCurrency::Bank.new
end

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

Call the following regularly in a scheduled job:

ActiveCurrency::AddRates.call(currencies: %w[EUR USD])

The first currency you give in currencies is considered the default currency against which other currency rates will be guessed if they are unavailable.

By defaut it uses the eu_central_bank to fill the currency rates.

To use the money-open-exchange-rates gem, add the gem to your Gemfile, then add the following to your application’s initializers:

ActiveCurrency.configure do |config|
  config.remote_bank = :open_exchange_rates
  config.open_exchange_rates_app_id = '…'
end

You can provide any Money-compatible bank when calling ActiveCurrency::AddRates:

ActiveCurrency::AddRates.call(…, bank: …)

If you want to increase or decrease the currency rates by a given multiplier, you can do so by setting the multiplier option:

ActiveCurrency.configure do |config|
  config.multiplier = {
    ["EUR", "USD"] => 1.01,
  }
end

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 use a fake rate store in your rails_helper.rb:

MoneyRails.configure do |config|
  rate_store = Money::RatesStore::Memory.new.tap do |store|
    store.add_rate('USD', 'EUR', 1.5)
    store.add_rate('EUR', 'USD', 0.67)
  end
  config.default_bank = Money::Bank::VariableExchange.new(rate_store)
end

Please file issues and pull requests on GitHub.

Install:

BUNDLE_GEMFILE=Gemfile-rails7.0 bundle install

Launch specs and linters:

BUNDLE_GEMFILE=Gemfile-rails7.0 bin/rake

Update CHANGELOG.md, update version in lib/active_currency/version.rb.

Then:

BUNDLE_GEMFILE=Gemfile-rails6.1 bundle update
BUNDLE_GEMFILE=Gemfile-rails7.0 bundle update

git add CHANGELOG.md lib/active_currency/version.rb Gemfile-rails*
git commit -m v`ruby -r./lib/active_currency/version <<< 'puts ActiveCurrency::VERSION'`
bin/rake release

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