Money Persistent Bank
"Money" gem provides VariableExchange which is useful for converting money from one currency to another. This gem provides PersistentBank which can save rates to a local storage and automatically load from it in another place.
This can be useful in a Rails application. You fetch rates from external source once a day in a rake task and your running application picks up the new rates on the next request.
Usage in Rails
Add it to your gemfile:
gem "money_persistent_bank", "~> 0.2.0"
Now you can use it in a rake task.
task :fetch_rates => :environment do bank = Money.default_bank # Here goes your code that fetches the rates from external source. # Emulating this: sleep 1 bank.set_rate(:usd, :eur, 0.8) bank.export_rates # you have to explicitly export after setting the rates end
(See also money_bank_sources.)
And somewhere in your application:
Money.default_bank.import_rates 1.to_money(:usd).exchange_to(:eur).to_f # => 0.8
When the rates are updated it will automatically use them.