我创建了一个带有会话对象中存在的线条项目的购物车。 我无法理解我如何连接到购物车显示页面, 如果该手车存在的话, 只要链接到一个手车是空的页面, 如果它不存在的话。 我错过了什么? 我的代码如下:

• Cart has_many line_items, & lineitems belongs to Cart

View Link , I wasn t sure what I should put here and where to define it for example... "if current_cart.empty? cart", or "if @cart.line_items.empty? current_cart", etc.

        <% if current_cart.line_items.empty?%>
        <%= link_to "cart", cart_path, :class => headertab  %>&nbsp;
    <% else %>
        <%= link_to "cart", cart_path(current_cart), :class => headertab  %>&nbsp;
    <% end %>

这给了我以下错误:

Showing /Users/dave/rails_projects/EquiptMe/app/views/layouts/_headerexterior.html.erb where line #20 raised:

undefined local variable or method `current_cart  for #<#<Class:0x007fae841cc8e0>:0x007fae83339698>
Extracted source (around line #20):

17:         <li><%= link_to "browse gear",  /gear , :class => headertab  %></li>
18:         <li><%= link_to "join",  /signup , :class => headertab  %></li>
19:         <li>
20:         <% if current_cart.line_items.empty?%>
21:             <%= link_to "cart", cart_path, :class => headertab  %>&nbsp;
22:         <% else %>
23:             <%= link_to "cart", cart_path(current_cart), :class => headertab  %>&nbsp;

<强 > 运行

Outdoor::Application.routes.draw do
  resources :line_items

  resources :carts
.....

<强 > 应用控制器

class ApplicationController < ActionController::Base
  protect_from_forgery

  private

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

< 坚固> 电源控制器“ 显示 ”, “ 销毁” & amp; “ 创建”

 def show
    begin
    @cart = Cart.find(params[:id])
    rescue ActiveRecord::RecordNotFound
      logger.error "Attempt to access invalid cart #{params[:id]}"
      redirect_to  /gear , notice:  Invalid cart 
    else
      respond_to do |format|
        format.html # show.html.erb
        format.json { render json: @cart }
      end
   end

  def destroy
    @cart = current_cart
    @cart.destroy
    session[:cart_id] = nil

    respond_to do |format|
      format.html { redirect_to carts_url, notice:  Your cart is currently empty  }
      format.json { head :no_content }
    end
end

  def create
    @cart = Cart.new(params[:cart])

    respond_to do |format|
      if @cart.save
        format.html { redirect_to @cart, notice:  Cart was successfully created.  }
        format.json { render json: @cart, status: :created, location: @cart }
      else
        format.html { render action: "new" }
        format.json { render json: @cart.errors, status: :unprocessable_entity }
      end
    end
  end

< 坚固 > 列项目控制器“ 创建”

 def create
    @cart = current_cart
    gear = Gear.find(params[:gear_id])
    @line_item = @cart.add_gear(gear.id)

    respond_to do |format|
      if @line_item.save
        format.html { redirect_to @line_item.cart }
        format.json { render json: @line_item, status: :created, location: @line_item }
      else
        format.html { render action: "new" }
        format.json { render json: @line_item.errors, status: :unprocessable_entity }
      end
    end
  end
  end

感谢您的帮助! < 强/ 强 >