attribute-depends-calculator | Automatically calculate a collection of depends | Application Framework library

class Order < ActiveRecord::Base
  has_many :order_items
  depend total_price: {order_items: :price, operator: :+} # or :*
end

class Order < ActiveRecord::Base
  ...
  depend total_price: {order_items: :price, operator: :sum} # default
end

cl  

class Order < ActiveRecord::Base
  has_many :order_items
  depend total_price: {order_items: :price}
end

class OrderItem < ActiveRecord::Base
  belongs_to :order
end

order = Order.first
order.total_price
#=> 100.0
order.order_items.pluck(: