Question

I have what I am sure is a nooby question…

I have a view where I am showing a list of products delivered to customers. I used a couple of Ryan Bates’ railscasts as models for having a search field and sortable columns plus pagination.

Pagination and Search work fine. However, I have two issues that I can’t seem to find:

1) If I try and show the name of the customer, instead of their ID, for a product, I get an error saying the ‘name’ method is not defined.

2) When I click on the column heading to change the sort order, nothing happens.

Here is my code:

Products Controller:

class ProductsController < ApplicationController
  # GET /products
  # GET /products.json

  helper_method :sort_column, :sort_direction

  def index
    @products = Product.search(params[:search]).order(sort_column + " " +    sort_direction).paginate(:per_page => 25, :page => params[:page])

    respond_to do |format|
      format.html # index.html.erb
      format.json { render json: @products }
    end
  end
  .
  .
  .
 private
   def sort_column
    Product.column_names.include?(params[:sort]) ? params[:sort] : "name"
   end

  def sort_direction
    %w[asc desc].include?(params[:direction]) ? params[:direction] : "asc"
  end
end

Products Model:

# == Schema Information
#
# Table name: products
#
#  id             :integer(4)      not null, primary key
#  name           :string(255)
#  serial_number  :string(255)
#  date_ordered   :date
#  date_received  :date
#  date_invoiced  :date
#  vendor_invoice :string(255)
#  scc_invoice    :string(255)
#  quantity       :integer(10)
#  dollar_amount  :integer(10)
#  warranty_years :integer(4)
#  warranty_days  :integer(4)
#  item           :integer(4)
#  comments       :text
#  created_at     :datetime        not null
#  updated_at     :datetime        not null
#  vendor_id      :integer(4)
#  customer_id    :integer(4)
#  category_id    :integer(4)
#  department     :string(255)
#

class Product < ActiveRecord::Base
  attr_protected :id

  belongs_to :customer
  belongs_to :vendor
  belongs_to :category

  def self.search(search)
      if search
          where('name LIKE ?', "%#{search}%")
      else
          scoped
      end
  end
end

Product Index View:

<% title "Products" %>

<%= form_tag products_path, :method => 'get', :id => "products_search" do %>
    <p>
        <%= text_field_tag :search, params[:search] %>
        <%= submit_tag "Search", :name => nil%>
    </p>
    <div id="products"><%= render 'products' %></div>
<% end %>

<p><%= link_to 'Add Product', new_product_path %></p>

Products partial view: _products.html.erb

<%= hidden_field_tag :direction, params[:direction] %>
<%= hidden_field_tag :sort, params[:sort] %>

<table class="pretty">

  <tr>
    <th><%= sortable "name" %></th>
    <th><%= sortable "serial_number" %> </th>
    <th><%= sortable "date_invoiced" %></th>
    <th>Scc invoice</th>
    <th>Customer</th>
    <th></th>
    <th></th>
  </tr>

  <% for product in @products %>

  <tr>
    <td><%= product.name %></td>
    <td><%= product.serial_number %></td>
    <td><%= product.date_invoiced %></td>
    <td><%= product.scc_invoice %></td>
    <td><%= product.customer.name %></td>
    <td><%= link_to 'Show', product %></td>
    <td><%= link_to 'Edit', edit_product_path(product) %></td>
  </tr>

<% end %>

<%= will_paginate @products %>

I am not sure what else someone might need to get an idea of what is on so let me know if there is more information needed.

Here is what I see on the server when it runs:

Started GET “/products” for 127.0.0.1 at 2012-06-27 14:04:11 -0600
Connecting to database specified by database.yml
Processing by ProductsController#index as HTML
←[1m←[36mProduct Load (60.0ms)←[0m ←[1mSELECT products.* FROM products ORDER BY name asc LIMIT 25 OFFSET 0←[0m
←[1m←[35m (0.0ms)←[0m SELECT COUNT() FROM products
←[1m←[36mCustomer Load (0.0ms)←[0m ←[1mSELECT customers. FROM customers WHERE customers.id = 0 LIMIT 1←[0m
Rendered products/_products.html.erb (535.0ms)
Rendered products/index.html.erb within layouts/application (660.0ms)
Completed 500 Internal Server Error in 895ms

ActionView::Template::Error (undefined method name' for nil:NilClass):
20: <td><%= product.serial_number %></td>
21: <td><%= product.date_invoiced %></td>
22: <td><%= product.scc_invoice %></td>
23: <td><%= product.customer.name unless product.customer.name.nil? %></td>
24: <td><%= link_to 'Show', product %></td>
25: <td><%= link_to 'Edit', edit_product_path(product) %></td>
26: </tr>
app/views/products/_products.html.erb:23:inblock in _app_views_products__products_html_erb__429528032_35444568′
app/views/products/_products.html.erb:16:in _app_views_products__products_html_erb__429528032_35444568'
app/views/products/index.html.erb:8:inblock in _app_views_products_index_html_erb___506300995_27575616′
app/views/products/index.html.erb:3:in _app_views_products_index_html_erb___506300995_27575616'
app/controllers/products_controller.rb:11:inindex’

Rendered C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/actionpack-3.2.5/lib/action_dispatch/middleware/template
s/rescues/_trace.erb (5.0ms)
Rendered C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/actionpack-3.2.5/lib/action_dispatch/middleware/template
s/rescues/_request_and_response.erb (5.0ms)
Rendered C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/actionpack-3.2.5/lib/action_dispatch/middleware/template
s/rescues/template_error.erb within rescues/layout (65.0ms)

Answer 1

OK from your stacktrace we can see that:

name' for nil:NilClass)

This means your customer object is null. So the SQL is not returning a customer object attached to your products objects.

your code here:

<%= product.customer.name unless product.customer.name.nil? %>

does not catch it since you are testing the nil on the name attribute, not the customer object

<%= product.customer.name unless product.customer.nil? %>

This should fix the error, but you still wont see the customer name!

To really fix your problem, you have to verify your relationship between Products and Customers in your model code and debug the SQL you get from it to be sure to see a JOIN between products and customer.

Check to see if you have a has_many : products declared in customer object.

UPDATE: I also see in your product model that you declared the customer_id in the product table?! That means your Products can only have 1 customer!!! Not sure it is what you want! 😉

here is a link on the rails guide to relationship, it was my bible when i worked with rails

UPDATE 2
After reviewing the Active Record Query interface, to get what i think you want, you should do something like that:

Products.joins(:customer).where("name like ?", %#{search}%)