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Integration of RubyMoney - Money with Rails
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RubyMoney - Money-Rails

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This library provides integration of money gem with Rails.

Use 'monetize' to specify which fields you want to be backed by Money objects and helpers provided by the money gem.

Currently, this library is in active development mode, so if you would like to have a new feature feel free to open a new issue here. You are also welcome to contribute to the project.


Add this line to your application's Gemfile:

gem 'money-rails'

And then execute:

$ bundle

Or install it yourself as:

$ gem install money-rails

You may also install money configuration initializer:

$ rails g money_rails:initializer

There, you can define the default currency value and set other configuration parameters for the rails app.


For example, we create a Product model which has an integer price_cents column and we want to handle it by using a Money object instead:

class Product < ActiveRecord::Base

  monetize :price_cents


Now each Product object will also have an attribute called price which is a Money object and can be used for money comparisons, conversions etc.

In this case the name of the money attribute is created automagically by removing the _cents suffix of the column name.

If you are using another db column name or you prefer another name for the money attribute, then you can provide as argument with a string value to the monetize macro:

monetize :discount_subunit, :as => "discount"

Now the model objects will have a discount attribute which is a Money object, wrapping the value of discount_subunit column to a Money instance.


Money-rails supports a set of options to handle currencies for your monetized fields. The default option for every conversion is to use the global default currency of Money library, as given in the configuration initializer of money-rails:

# config/initializers/money.rb
MoneyRails.configure do |config|

  # set the default currency
  config.default_currency = :usd


In many cases this is not enough, so there are some other options to satisfy your needs.

Model Currency

You can define a specific currency for an activerecord model. This currency is used for the creation and conversions of the Money objects referring to every monetized attributes of the specific model. This means it overrides the global default currency of Money library. To attach a currency to a model use the register_currency macro:

# app/models/product.rb
class Product < ActiveRecord::Base

  # Use EUR as model level currency
  register_currency :eur

  monetize :discount_subunit, :as => "discount"
  monetize :bonus_cents


Now and product.bonus will return a Money object using EUR as currency, instead of the default USD.

Attribute Currency (:with_currency)

By using the key :with_currency with a currency symbol value in the monetize macro call, you can define a currency in a more granular way. This way you attach a currency only to the specific monetized model attribute. It also allows to override both the model level and the global default currency:

# app/models/product.rb
class Product < ActiveRecord::Base

  # Use EUR as model level currency
  register_currency :eur

  monetize :discount_subunit, :as => "discount"
  monetize :bonus_cents, :with_currency => :gbp


In this case the product.bonus will return a Money object of GBP currency, whereas # => EUR

Instance Currencies

All the previous options do not require any extra model field to hold currency values. If you need to provide differrent currency per model instance, then you need to add a column with the name currency in your db table. Money-rails will discover this automatically, and will use this knowledge to override the model level and global default values. Attribute currency cannot be combined with instance currency!

class Transaction < ActiveRecord::Base

  # This model has a separate currency column
  attr_accessible :amount_cents, :currency, :tax_cents

  # Use model level currency
  register_currency :gbp

  monetize :amount_cents
  monetize :tax_cents


# Now instantiating with a specific currency overrides the
# the model and global currencies
t = => 2500, :currency => "CAD")
t.amount ==, "CAD") # true

WARNING: In this case :with_currency is not permitted and the usage of this parameter will cause an ArgumentError exception.

In general, the use of this strategy is discouraged unless there is a reason.

Configuration parameters

You can handle a bunch of configuration params through money.rb initializer:

MoneyRails.configure do |config|

  # To set the default currency
  config.default_currency = :usd

  # Add custom exchange rates
  config.add_rate "USD", "CAD", 1.24515
  config.add_rate "CAD", "USD", 0.803115

  # To handle the inclusion of validations for monetized fields
  # The default value is true
  config.include_validations = true

  # Register a custom currency
  # config.register_currency = {
  #   :priority            => 1,
  #   :iso_code            => "EU4",
  #   :name                => "Euro with subunit of 4 digits",
  #   :symbol              => "€",
  #   :symbol_first        => true,
  #   :subunit             => "Subcent",
  #   :subunit_to_unit     => 10000,
  #   :thousands_separator => ".",
  #   :decimal_mark        => ","
  # }
  • default_currecy: Set the default (application wide) currency (USD is the default)
  • include_validations: Permit the inclusion of a validates_numericality_of validation for each monetized field (the default is true)
  • register_currency: Register one custom currency. This option can be used more than once to set more custom currencies. The value should be a hash of all the necessary key/value pairs (important keys: :priority, :iso_code, :name, :symbol, :symbol_first, :subunit, :subunit_to_unit, :thousands_separator, :decimal_mark).
  • add_rate: Provide custom exchange rate for currencies in one direction only! This rate is added to the attached bank object.
  • default_bank: The default bank object holding exchange rates etc. (



MIT License. Copyright 2012 RubyMoney.

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