This library makes it easier to deal with Money values, storing them as integers to avoid floating-point math errors.
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.
Two const class variables are available to tailor Money to your needs. If you don't need currency exchange at all, just ignore those.
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.
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)