Rails，从2名佣工处获得折扣金额

Question

我有一家小型的铁路店，并且帮助者计算总价和折扣（如果已应用），但我想确定实际折扣显示在视图 -

def total_price 
    price = 0 
    order_products.each do |order_products| 
     # add the item price to total 
     price += (order_products.price_in_pence * order_products.quantity) 
    end 
    apply_discount(price) 
    end 

    def apply_discount(price) 
    return price if discount.nil? 
    if discount.percentage.present? 
     price = price - ((price/100) * discount.percentage) 
    elsif discount.money.present? 
     price = price - discount.money 
    end 
    price < 0 ? 0 : price 
    end 

    def discount_amount 
    I need something here to take the total_price from above 
    before a discount and then the apply_discount and subtract the 2. 
    end 

Answer 1

你应该重构折扣前的价格为私有方法重用：

def total_price  
    apply_discount(price_before_discount) 
    end 

    def apply_discount(price) 
    return price if discount.nil? 
    if discount.percentage.present? 
     price = price - ((price/100) * discount.percentage) 
    elsif discount.money.present? 
     price = price - discount.money 
    end 
    price < 0 ? 0 : price 
    end 

    def discount_amount 
    price_before_discount - total_price 
    end 

    private 
    def price_before_discount 
     @price_before_discount ||= order_products.inject(0) do |sum, order_product| 
     # add the item price to total 
     sum += (order_product.price_in_pence * order_product.quantity) 
     end 
    end 

Answer 2

不知道你在哪里从apply_discount越来越discount，但好像你要提供四个值在我看来：

• 价格
• 折扣率
• 平折
• 总

所以，也许这样的事情？

def price 
    order_productions.each { |p| p.price * p.quantity } 
end 

def percent_discount 
    1 - (discount.percentage || 0) # ie, 100% [or 0% off] when discount.percentage is nil 
end 

def flat_discount 
    discount.money || 0 # (ie, 0 dollars off) 
end 

def total 
    [(price * percent_discount) - flat_discount, 0].max # to ensure we get a positive value 
end 

（注：未经测试）

（您可能需要调整位的情况下，[如果是下]一个折扣既有百分比并在其上固定金额，或者如果折扣可以为空）

Answer 3

我将移动计算到discount_amount方法：

def total_price 
    order_products.inject(0) do |sum, product| 
    sum + (product.price_in_pence * product.quantity) 
    end 
end 

def discount_amount 
    return 0 unless discount 
    if discount.percentage.present? 
    (total_price/100) * discount.percentage 
    elsif discount.money.present? 
    discount.money 
    end 
end 

def total_price_after_discount 
    total_price - discount_amount 
end