Question

    def remove_items
    line_items.each do |item|
        @ci = Product.find(item.id)
        @ci.quantity = @ci.quantity.to_i - 1
end

您好，我正在尝试使用该项的ID，然后将该ID与产品匹配，然后将-1减去该产品的数量属性。

我目前收到此错误。

TypeError in OrdersController#create

can't convert nil into String

有什么问题？感谢

OrderController＃创建请记住，由于正在进行，代码很邋.. ：）

def create
@order = current_cart.build_order(params[:order])
@order.ip_address = request.remote_ip
@cart = current_cart

  if @order.save
      if @order.purchase
        @order.status = "paid"                      
        @cart.remove_items          
        @cart.destroy
        render :action => "success"
      else
      @order.status = "failed"
      @cart.destroy
         render :action => "failure"
    end
  else
    render action: "new"        
  end

端

我认为这是堆栈跟踪

[0m
  ←[1m←[35mLineItem Load (0.0ms)←[0m  SELECT "line_items".* FROM "line_items" WH
ERE "line_items"."cart_id" = 129
  ←[1m←[36mProduct Load (0.0ms)←[0m  ←[1mSELECT "products".* FROM "products" WHE
RE "products"."id" = ? LIMIT 1←[0m  [["id", 147]]
Completed 500 Internal Server Error in 5762ms

TypeError (can't convert nil into String):
  app/controllers/application_controller.rb:60:in `+'
  app/controllers/application_controller.rb:60:in `record_not_found'

Answer 1

根据你的评论，这应该可以解决问题：

# application_controller.rb
def record_not_found
  flash[:alert] = "Cannot find record number #{params[:id]}. Displaying all records." 
  redirect_to root_path 
end

但如果我是你，我不会在警告信息中输出params [：id]。只是说没有找到记录，basta。

flash[:alert] = "Cannot find record. Displaying all records."

您也可以在一行中执行此操作：

redirect_to root_path, alert: "Cannot find record. Displaying all records."

要修复remove_items方法中的逻辑，您需要在最后实际保存对象：

def remove_items
    line_items.each do |item|
        ci = Product.find(item.id)
        ci.quantity = ci.quantity.to_i - 1
        ci.save
    end
end

Answer 2

看起来您正在从头开始构建购物车应用。您是否考虑过使用Spree等现有平台？

Answer 3

让DB一次性减少所有产品是个更好的主意：

def remove_items
    Product.where(id:line_items.map(&:id)).update_all('quantity = quantity - 1')
end

或更好：

def remove_items
    Product.decrement_counter(:quantity, line_items.map(&:id) )
end

如果无法找到产品，这些会更快，避免错误，如果您同时运行多个进程，也可以避免Race Condition。

ruby on rails查询

3 个答案: