Modules vs method objects

method_object.rb

class OrderPriceCalculation
  def initialize(order, tax_rate:)
    @order = order
    @tax_rate = tax_rate
  end

  def total
    subtotal + sales_tax + fees
  end

  def subtotal
    items
      .map(&:price)
      .reduce(0, :+)
  end

  def sales_tax
    items
      .select(&:taxable?)
      .map { |o| o.price * @tax_rate }
      .reduce(0, :+)
  end

  def fees
    delivery_fee + processing_fee
  end

  def delivery_fee
    if @order.delivery?
      3.99
    else
      0
    end
  end

  def processing_fee
    0.30
  end

  def items
    @order.line_items
  end
end

module.rb

module CalculateOrderPrice
  module_function

  def total(order, tax_rate:)
    subtotal(order) + sales_tax(order, tax_rate) + fees(order)
  end

  def subtotal(order)
    items
      .map(&:price)
      .reduce(0, :+)
  end

  def sales_tax(order, rate)
    order
      .line_items
      .select(&:taxable?)
      .map { |o| o.price * rate }
      .reduce(0, :+)
  end

  def fees(order)
    delivery_fee(order) + processing_fee
  end

  def delivery_fee(order)
    if order.delivery?
      3.99
    else
      0
    end
  end

  def processing_fee
    0.30
  end
end