steveluscher-money

== Money

This library makes it easier to deal with Money values, storing them as integers to avoid floating-point math errors.

== Download

Preferred method of installation is gem:

gem install --source http://gems.github.com collectiveidea-money

You can find the source at:

http://github.com/collectiveidea/money

== Rails

There is a rails extension that makes it easier to store money values in the database.

class Product < ActiveRecord::Base money :price validates_numericality_of :price_in_cents, :greater_than => 0 end

This assumes that there is a price_in_cents (integer) column in the database, which can be changed by passing the :cents option. You can also specify the :currency option to save the currency to a field in the database.

class Room < ActiveRecord::Base money :rate, :cents => :rate_cents, :currency => :rate_currency money :discount, :cents => :discount_cents end

You can set the attribute to a String, Fixnum, or Float and it will call #to_money to convert it to a Money object. This makes it convenient for using money fields in forms.

r = Room.new :rate => "100.00" r.rate # returns <Money:0x249ef9c @currency="USD", @cents=10000>

By default, money values will be stored with a precision of 2 (cents). If you need to store different precisions, such as to the nearest tenth of a cent, you can specify the +:precision+ option:

class Room < ActiveRecord::Base money :rate, :precision => 3 end

r = Room.new :rate => "100" r.rate.format # returns $100.000 r.rate = "100.995" r.rate.format # returns $100.995

To use the Rails functionality, install money as a plugin, or require 'money/rails'. This version is compatible with Rails 2.2. For compatibility with previous versions of Rails, check out the rails-2.1 branch.

== 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