RubyMoney/money-rails — pull request #33 by joeframbach (2012-08-13 15:16:42+00:00)
Title: Allow methods to be monetized

For example:

class User < ActiveRecord::Base
monetize :balance_cents
def balance_cents(other_user)
# return number of cents this user owes that user
end
end

Now `joe.balance(bob)` will return a Money object with value `joe.balance_cents(bob)`.