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: github.com/samlown/money

• Previous fork: github.com/ShadowBelmolve/money

• Website: money.rubyforge.org

• RDoc API: money.rubyforge.org

• Git repository: 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 samlown-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

# Comparisons with other numbers
Money.new(10.10) > 10.0     # => true
Money.new(1001) > 10        # => true
Money.new(999) > 10         # => 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("CAD", 0.803115)
Money.add_rate("USD", 1.24515)

Money.us_dollar(100_00).exchange_to("CAD")  # => Money.new(15504, "CAD")
Money.ca_dollar(100_00).exchange_to("USD")  # => Money.new(6450, "USD")

or

Money.us_dollar(100).as_cad              # => Money.new(155, "CAD")
Money.ca_dollar(100).as_usd              # => Money.new(64, "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("EUR", 0.5)
Money.new(1000, "EUR") + Money.new(1000, "USD") == Money.new(1500, "EUR")

Fetch the exchange rates published by the European Bank

Money.default_bank.fetch_rates          # Fetch the rates
Money.default_bank.auto_fetch 3600      # Fetch the rates every hour
Money.default_bank.stop_fetch           # Stop auto-fetch

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

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 'ShadowBelmolve-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