many to many

I am trying to create an on line store and i would like to have the shopper select by category. i have established the many to many relationship between product and category, but I don't believe that I am calling it out in the controller properly. What should I be using in the index action in the category controller to recognize products?

okay, so then when I am trying to call the products like this.

<h1>Listing categories</h1>

<table>
  <tr>
    <th>Parent</th>
    <th>Name</th>
  </tr>

<% @categories.each do |category| %>
  <tr>
    <td><%=h category.parent_id %></td>
    <td><%=h category.name %></td>
    <td><%=h category.product.image_url %>
    <td><%= link_to 'Show', category %></td>
    <td><%= link_to 'Edit', edit_category_path(category) %></td>
    <td><%= link_to 'Destroy', category, :confirm => 'Are you sure?', :method => :delete %></td>
  </tr>
<% end %>
</table>
<%= render(:partial => "show_products_by_category", :object => @product) %>

<br />

<%= link_to 'New category', new_category_path %>

I get this error message?

.... error message?

Post your show action, too, please.

uninitialized constant Category::CategoriesProduct

 is my error message.  I am wondering if it is something in the model or route?

This is my model for Category

class Category < ActiveRecord::Base

  has_many :categories_products
  has_many :products, :through => :categories_products
 

This is my show action.  

 def show
    @category = Category.find(params[:id])
    @product = Product.find(params[:id])
  @products = Category.find(params[:id]).products

    respond_to do |format|
      format.html # show.html.erb
      format.xml  { render :xml => @category }
    end
  end


Thank you for your help!

Can you post your CategoriesProducts model?

class Categories_Products
  belongs_to :product
  belongs_to :category
 
  def initialize
   
  end
end


this is what I have in the model.  thanks again

Okay, that looks all right, but you might have a pluralization issue.
has_many products => looks for "Product" model.
has_many category_products => looks for "CategoriesProduct" (no s) model?

The joined table name is more for use with a HABTM relationship.  Normally a :through join model has its own name (Readers -- Subscriptions -- Magazines OR Books -- Authorships -- Authors)

So, you might change the filename (categories_product.rb) AND(!) the class name (CategoriesProduct) and try that.  Or change to a more descriptive join model or just use HABTM.

You can test the relationship in the console:

ruby script/console

c = Category.find(:first)
c.categories_product
# => should return array of CategoriesProducts records

... and so on

that is interesting about the pluralization.  i tried to follow this from another example.  do you think it is better to use habtm?  if so, do i not use a model?  

also I am trying to have a category that displays many products.  wouldn't it be a category_products pluralization?  thanks for your help I can't believe how confusing this is.

I go with the simplest solution that fits the bill.

Do you need to access more information on the join model?  Using the Reader -- Subscription -- Magazine example, a subscription has more information about the relationship, like start date and number of issues purchased.  So, it should be has_many :through!

If you don't need that extra information, use HABTM.  Simple, easy.
http://www.railsbrain.com/api/rails-2.3.2/doc/index.html?a=M001888&name=has_and_belongs_to_many

With HABTM, the table would be categories_products (both pluralized, alphabetical) and you would delete the join model.  You'd need to remove the "id" column from the join table, too!

create_table :categories_products, :id => false do |t|
  ...

You *could* override the table name, but I wouldn't:
has_and_belongs_to_many :products, :join_table => "cat_prod"

Join models are definitely confusing the first time you use them.  The console is your friend!  You can get in there and try out stuff at the model level easily.

Wes,

You have helped me a lot and i reviewed what I had.  It turns out that my categories_products, did not have test data in it.  When I added it, I got it to work.  Once, I did that, the products appeared on the categories show page, no problems.  Thanks!