Question

我正在做我的第一个关于铁路项目的红宝石，并且显示“ nil：NilClass的未定义方法'title'”错误。

这是密码

============ index.html.erb =======

        <table>
         <% @products.select {|p| p.price.to_i > 200 }.each do |product|%>
         <tr>
            <td><%= product.title %></td>
            <td><%= product.price %></td>

         </tr>
         <% end %>
       </table>

============= products_controller.rb =========

      class ProductsController < ApplicationController
      def index
          @products = Product.all
       end

       def show
          if params[:id] == "ALL"
             @products = Product.all
          else
             @product = Product.find(params[:id])
          end

               Prefix Verb   URI Pattern                                                                              Controller#Action
        welcome_index GET    /welcome/index(.:format)                                                                 welcome#index
             products GET    /products(.:format)                                                                      products#index
                      POST   /products(.:format)                                                                      products#create
          new_product GET    /products/new(.:format)                                                                  products#new
         edit_product GET    /products/:id/edit(.:format)                                                             products#edit
              product GET    /products/:id(.:format)                                                                  products#show
                      PATCH  /products/:id(.:format)                                                                  products#update
                      PUT    /products/:id(.:format)                                                                  products#update
                      DELETE /products/:id(.:format)                                                                  products#destroy
                 root GET    /                                                                                        welcome#index

=============

我要做的就是如果参数为“ ALL”则显示所有产品，如果参数为“ ONSALE”则显示某些产品（价格<50），以及当参数为产品ID时显示单个产品。欢迎任何建议！

Answer 1

如果我阅读了您的源代码，似乎您只需要列出价格高于200的产品您可以使用 where 进行操作，稍后，如果您想更进一步地过滤数据，则可以学习ransack gem

为您的 index.html.erb

<table>
  <% @products.each do |product| %>
    <tr>
      <td><%= product.title %></td>
      <td><%= product.price %></td>
    </tr>
  <% end %>
</table>

这是您的 ProductsController

class ProductsController < ApplicationController
  def index
    # if you want directly to filter just the list product that has price above 200 
    # then you can use where, your view just to show the result of @products

    @products = Product.where('price > ?',200)
  end
end

Ruby on Rails错误：nil：NilClass

1 个答案: