Question

我有这种方法来检查优惠券是否有效。我想在优惠券有效时更新current_cart中的总金额。目前我收到此错误NoMethodError in CouponsController#redeem undefined method amount for nil:NilClass

关于可能出错的任何想法？

coupons_controller.rb

UPDATE4

 def redeem
     @coupon = Coupon.find_by_discount_code(params[:discount_code])
  if @coupon.blank?
     redirect_to :back
     flash[:notice] = "Coupon is Invalid!"
  else 
     @current_cart = Cart.find(current_cart.id)
     @current_cart.amount = current_cart.amount - @coupon.amount
     current_cart.save
     redirect_to :back
     flash[:notice] = "Coupon is Valid!"
  end
end

更新1

application_controller.rb

  def current_cart 
    Cart.find(session[:cart_id])
  rescue ActiveRecord::RecordNotFound 
    cart = Cart.create 
    session[:cart_id] = cart.id
    cart
  end

  helper_method :current_cart
end

UPDATE3

class Cart < ApplicationRecord
  has_many :line_items, dependent: :destroy

  def add_product(product_id)
    current_item = line_items.find_by_product_id(product_id) 
    if current_item
      current_item.quantity += 1
    else
      current_item = line_items.build(product_id: product_id)
    end
    current_item
  end


  def total_price
    line_items.to_a.sum { |item| item.total_price }
  end

  def tax_rate
    tax_amount = 0 
    line_items.each do |item|
      tax_amount += (item.product.price * item.quantity) * item.product.tax_rate.rate
    end
    tax_amount
  end    

  def amount
    line_items.to_a.sum { |item| item.total_price } + tax_rate + fee
  end

  def fee
    shipment_amount = 0 
    line_items.each do |item|
      if item.quantity <= 1
        shipment_amount = item.product.shipment.fee
      else
        shipment_amount = item.product.multiple_shipment.fee
      end
    end
    shipment_amount
  end
end

车/ show.html.erb

<%= number_to_currency current_cart.amount %>

Answer 1

使用blank?方法，例如：

def redeem
  @coupon = Coupon.find_by_discount_code(params[:discount_code])
  if @coupon.blank?
   redirect_to :back
   flash[:notice] = "Coupon is Invalid!"
  else 
   current_cart.amount = current_cart.amount - @coupon.amount
   redirect_to :back
   flash[:notice] = "Coupon is Valid!"
  end
end

Answer 2

试试这个

def redeem
    @coupon = Coupon.find_by_discount_code(params[:discount_code])
    if @coupon.blank?
      redirect_to :back
      flash[:notice] = "Coupon is Invalid!"
    else 
       @current_cart = Cart.find(current_cart.id)
       @current_cart.amount = @current_cart.amount - @coupon.amount
       @current_cart.save
       redirect_to :back
       flash[:notice] = "Coupon is Valid!"
    end
end

更新购物车金额

2 个答案: