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

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

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

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

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

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.

• Better validation (fix composed_of allow_nil)

• Interest (almost there..)

• Remote rate fetching