Ruby on rails - TypeError (预期数字)： app/models/order_item.rb：46：in 'only_3_items_in_30_days'

Question

我正在Rails中构建一个具有特定销售模型的商店。我需要允许用户每30天只添加3个项目到他的订单。30天计数器应该从添加第一个order_item开始。一旦30天到期，用户将能够添加3个订单。如果30天没有过去，例如，用户添加了两个order_item，他仍然可以在30天内再添加一个order_item。因此，如果用户试图添加超过3个项目，则显示错误消息，并忽略保存order_items到current_user的订单。

我的日志中出现了这个错误

TypeError (expected numeric):
  app/models/order_item.rb:46:in `only_3_items_in_30_days'

控制器:

class OrderItemsController < ApplicationController
 def create
     @item = OrderItem.new(order_item_params)
  session[:order_id] = current_order.id
  if @item.save
    respond_to do |format|
      format.js { flash[:notice] = "ORDER HAS BEEN CREATED." } 
    end
  else
    redirect_to root_path
  end 
end
end

  def update
    @order = current_order
    @order_item = @order.order_items.find(params[:id])
    @order_item.update_attributes(order_item_params)
    @order_items = @order.order_items
  end

  def destroy
    @order = current_order
    @order_item = @order.order_items.find(params[:id])
    @order_item.destroy
    @order_items = @order.order_items
  end

private
  def order_item_params
  base_params = params.require(:order_item)
                      .permit(:quantity, :product_id, :user_id)
  base_params.merge(order: current_order)
 end

order_item.rb

class OrderItem < ActiveRecord::Base
  belongs_to :product
  belongs_to :order
  validates :quantity, presence: true, numericality: { only_integer: true, greater_than: 0 }
  validate :product_present
  validate :order_present
validate :only_3_items_in_30_days
  before_save :finalize
  def unit_price
    if persisted?
      self[:unit_price]
    else
      product.price
    end
  end
  def total_price
    unit_price * quantity
  end
private
  def product_present
    if product.nil?
      errors.add(:product, "is not valid or is not active.")
    end
  end
  def order_present
    if order.nil?
      errors.add(:order, "is not a valid order.")
    end
  end
  def finalize
    self[:unit_price] = unit_price
    self[:total_price] = quantity * self[:unit_price]
  end

  def only_3_items_in_30_days
    now = Date.new
    days_since_first = now - order.first_item_added_at
    if order.order_items.count > 2 && days_since_first < 30
      errors.add(:base, 'only 3 items in 30 days are allowed')
    end
    true      # this is to make sure the validation chain is not broken in case the check fails
  end

end

Answer 1

看来你的问题是双重的。

首先，您要在第45行使用DateTime.current(这是谈论"now"的正确方式)

其次，错误实际上是说你不能减去日期和nil。所以你需要先检查所有内容

def only_3_items_in_30_days
  unless order.first_item_added_at
    return true #(or whatever you want to do in this case)
  end
  now = Time.current
  days_since_first = now - order.first_item_added_at
  ...