require 'date'
require 'ostruct'
 
class OrdersReport
  def initialize(orders, start_date, end_date)
    @orders = orders
    @start_date = start_date
    @end_date = end_date
  end
 
  def total_sales_within_date_range
    within_date_range = ->order{ order.placed_at.between?(@start_date, @end_date) }
    @orders.select(&within_date_range).sum(&:amount)
  end
 
end
 
class Array #for ideone.com
  def sum(zero = 0, &b)
    inject(zero){ | s, e | s + (b ? b[e] : e) }
  end
end
 
class Order < OpenStruct
end
 
order_within_range1 = Order.new(amount: 5,placed_at: Date.new(2016, 10, 10))
order_within_range2 = Order.new(amount: 10,placed_at: Date.new(2016, 10, 15))
order_out_of_range = Order.new(amount: 6,placed_at: Date.new(2016, 1, 1))
orders = [order_within_range1, order_within_range2, order_out_of_range]
 
start_date = Date.new(2016, 10, 1)
end_date = Date.new(2016, 10, 31)
 
report = OrdersReport.new(orders, start_date, end_date)
p report.total_sales_within_date_range #=> 15

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