WWR - Railsplugin: Money

Money

Money class

This money class is based on the example from the ActiveRecord doc: http://api.rubyonrails.org/classes/ActiveRecord/Aggregations/ClassMethods.html

Its in production use at http://www.snowdevil.ca and I haven't found any major issues so far. The main reason to open source it is because It might be useful to other people and I hope i'll get some feedback on how to improve the class.

I bundled the exporter with the money class since some tests depend on it and I figured that most applications which need to deal with Money also need to deal with proper exporting.

Download

Preferred method of installation is gem:

gem install --source http://dist.leetsoft.com money

Alternatively you can get the library packed

http://dist.leetsoft.com/pkg/

Usage

Use the compose_of helper to let active record deal with embedding the money object in your models. The following example requires a cents and a currency field.

class ProductUnit &lt; ActiveRecord::Base
  belongs_to :product
  composed_of :price, :class_name => "Money", :mapping => [%w(cents cents) %(currency currency)]
end

private        
  validate :cents_not_zero

def cents_not_zero
  errors.add("cents", "cannot be zero or less") unless cents > 0
end

validates_presence_of :sku, :currency
validates_uniqueness_of :sku

Class configuration

Two const class variables are available to tailor Money to your needs. If you don't need currency exchange at all, just ignore those.

= Default Currency

By default Money defaults to USD as its currency. This can be overwritten using

Money.default_currency = "CAD"

If you use rails, the environment.rb is a very good place to put this.

= Currency Exchange

The second parameter is a bit more complex. It lets you provide your own implementation of the currency exchange service. By default Money throws an exception when trying to call .exchange_to.

A second minimalist implementation is provided which lets you supply custom exchange rates:

Money.bank = VariableExchangeBank.new 
Money.bank.add_rate("USD", "CAD", 1.24515)
Money.bank.add_rate("CAD", "USD", 0.803115)
Money.us_dollar(100).exchange_to("CAD") => Money.ca_dollar(124)
Money.ca_dollar(100).exchange_to("USD") => Money.us_dollar(80)

There is nothing stopping you from creating bank objects which scrape www.xe.com for the current rates or just return rand(2)

== Code

If you have any improvements please email them to tobi [at] leetsoft.com