= Money $

This library aids one in handling money and different currencies. Features:

- Provides a Money class which encapsulates all information about an certain
  amount of money, such as its value and its currency.
- Represents monetary values as integers, in cents. This avoids floating point
  rounding errors.
- Provides APIs for exchanging money from one currency to another.
- Has the ability to parse a money string into a Money object.
- Provides ActiveRecord "has_money" method.

Resources:

- This fork: http://github.com/nofxx/money
- Website: http://money.rubyforge.org
- RDoc API: http://money.rubyforge.org
- Git repository: http://github.com/FooBarWidget/money/tree/master


== Download

Install stable releases with the following command:

  gem install money

The development version (hosted on Github) can be installed with:

  gem sources -a http://gems.github.com
  gem install nofxx-money


== Usage

=== Synopsis

  require 'money'

  # 10.00 USD
  money = Money.new(1000, "USD")
  money.cents     # => 1000
  money.currency  # => "USD"
  money.format    # => "$10.00"

  Money.new(880088, "EUR").format # => €8,800.88
  Money.new(-8000).format(:no_cents => true)  # => $-80

  Money.new(1000, "USD") == Money.new(1000, "USD")   # => true
  Money.new(1000, "USD") == Money.new( 100, "USD")   # => false
  Money.new(1000, "USD") == Money.new(1000, "EUR")   # => false


=== Currency Exchange

Exchanging money is performed through an exchange bank object. The default
exchange bank object requires one to manually specify the exchange rate. Here's
an example of how it works:

  Money.add_rate("USD", "CAD", 1.24515)
  Money.add_rate("CAD", "USD", 0.803115)

  Money.us_dollar(100).exchange_to("CAD")  # => Money.new(124, "CAD")
  Money.ca_dollar(100).exchange_to("USD")  # => Money.new(80, "USD")

or

  Money.us_dollar(100).to_cad              # => Money.new(124, "CAD")
  Money.ca_dollar(100).to_usd              # => Money.new(80, "USD")

Comparison and arithmetic operations work as expected:

  Money.new(1000, "USD") <=> Money.new(900, "USD")   # => 1; 9.00 USD is smaller
  Money.new(1000, "EUR") + Money.new(10, "EUR") == Money.new(1010, "EUR")

  Money.add_rate("USD", "EUR", 0.5)
  Money.new(1000, "EUR") + Money.new(1000, "USD") == Money.new(1500, "EUR")

There is nothing stopping you from creating bank objects which scrapes
www.xe.com for the current rates or just returns <tt>rand(2)</tt>:

  Money.default_bank = ExchangeBankWhichScrapesXeDotCom.new


=== Ruby on Rails

Use the +has_money+ method to embed the money object in your models.
The following example requires a +price_cents+ and a +price_currency+
fields on the database.

config/enviroment.rb

  require.gem 'nofxx-money', :lib => 'money'

app/models/product.rb

  class Product < ActiveRecord::Base
    belongs_to :product
    has_money :price

    validates_numericality_of :price_cents, :greater_than => 0
  end

migration:

  create_table :products do |t|
    t.integer :price_cents
    t.string  :price_currency
  end


=== Default Currency

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

  Money.default_currency = "CAD"

If you use Rails, then environment.rb is a very good place to put this.


== TODO

* Better validation (fix composed_of allow_nil)
* Interest (almost there..)
* Remote rate fetching