eeng/danconia

A very simple money library for Ruby

Danconia

A very simple money library for Ruby, backed by BigDecimal, with multi-currency support.

Features

• Backed by BigDecimal (no conversion to cents is done, i.e. "infinite precision")
• Multi-currency support
• Pluggable exchange rates services:
  • CurrencyLayer API
  • BNA
  • FixedRates (for testing use)
• Pluggable stores for persisting the exchange rates

Installation

gem 'danconia'

Basic Usage

If you only need to work with a single currency:

# USD by default, but can be configured
m1 = Money(10.25) # => 10.25 USD

# Note that we keep all decimal places
m2 = m1 / 2 # => 5.125 USD

# Simple formatting by default
puts m2 # => $5.13

Please refer to examples/single_currency.rb for some configuration options.

Multi-Currency Support

To handle multiple currencies you need to configure an Exchange in order to fetch the rates. For example, with CurrencyLayer:

# This can be placed in a Rails initializer
require 'danconia/exchanges/currency_layer'

Danconia.configure do |config|
  config.default_exchange = Danconia::Exchanges::CurrencyLayer.new(access_key: '...')
end

Then, download the exchange rates:

# You should do this periodically to keep rates up to date
Danconia.config.default_exchange.update_rates!

And finally to convert between currencies:

Money(9, 'JPY').exchange_to('ARS') # => 2.272401 ARS

By default, rates are stored in memory, but you can supply a store in the exchange constructor to save them elsewhere. Please refer to examples/currency_layer.rb for an ActiveRecord example.

Active Record Integration

Given a products table with a decimal column price and a string column price_currency (optional), then you can use the money class method to automatically convert it to Money:

require 'danconia/integrations/active_record'

class Product < ActiveRecord::Base
  money :price
end

Product.new(price: 30, price_currency: 'ARS').price # => 30 ARS

Currently, there is no option to customize the names of the columns but should be fairly simple to implement if needed.

Testing

There is a FixedRates exchange that can be used during testing to supply static rates (see examples/fixed_rates.rb). Another possibility is to use the following helper:

require 'danconia/test_helpers'

Danconia::TestHelpers.with_rates 'USDARS' => 3 do
  Money(2, 'USD').exchange_to('ARS') # => 6.0 ARS
end

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request