This gem helps you integrate Money fields into your ActiveRecord models without having to add new columns each time.
It also helps manage and sum various components of your models to keep amount definitions consistent across your application.
Add
gem 'amountable', github: 'instacart/amountable'
to your Gemfile
. Then run
bundle
and
rake amountable:install:migrations
and finally
rake db:migrate
Setup your model
class Order < ActiveRecord::Base
include Amountable
amount :subtotal, sets: [:total]
amount :delivery_fee, sets: [:total, :fees]
amount :bags_fee, sets: [:total, :fees]
amount :sales_tax, sets: [:total, :taxes]
amount :local_tax, sets: [:total, :taxes]
end
then create it
order = Order.create(
subtotal: Money.new(123),
delivery_fee: Money.new(100),
bags_fee: Money.new(10),
sales_tax: Money.new(56)
)
order.subtotal
# => #<Money fractional:123 currency:USD>
order.total
# => #<Money fractional:289 currency:USD>
order.fees
# => #<Money fractional:110 currency:USD>
order.taxes
# => #<Money fractional:56 currency:USD>
When you run the migration, an amounts
table will be created with a polymorphic relationship to an amountable
, which in the above example would be your orders.
When the an order is created with some amounts, the associated Amount
objects are persisted.
Amount
objects are persisted in bulk, so there are no N + 1 queries. If an amount is zero, no Amount
model is created.