Calculate sum of columns value in Ruby on Rails

Question

I want to calculate the sum of the values in a column. For example:

@items = Item.find_all_by_cart_id(cart)

Item has column quantity. I want the sum of the @items quantity.

Answer 1

Try this

@items = Item.find_all_by_cart_id(cart).sum(:quantity)

Answer 2

items_quantity = @items.map(&:quantity).sum