Products by Category

rubyonrails-talk
1

Hi,

I am trying to create a view where I can see all products that belong to a certain category. My models have the following relationships: Category: has_many :products Product: belongs_to :category

Both category_controller.rb and product_controller.rb are in my admin area and need Admin login to edit/delete...

I am also using a catalog_controller.rb to view all my products. In my catalog_controller.rb I created the following:

33. def categories 34. @page_title = "Categories" 35. @category_pages, @categories = paginate :categories, :per_page => 10 36. end 37. 38. def products_by_category 39. @category = Category.find(params[:id]) 40. @page_title = @category.name 41. @products = Category.products.find(:all) 42. end

So, If I go to /catalog/categories, I can see a list of links to all my categories. My views/catalog/categories.rhtml has this code:   <ul id="categories">     <% for category in @categories %>     <li><%= link_to category.name, :action => "products_by_category", :id => category %></li>     <% end %>   </ul>

My views/catalog/products_by_category.rhtml has this code: <% if category.products? %> <p>No Products found for this category</p> <% else %> <ul id="products">   <% for product in @products %>   <li><%= link_to product.title, :action => "show", :id => product %></

  <% end %> </ul> <% end>

But when I click on the category link, I get a NoMethodError in CatalogController#products_by_category:

undefined method `products' for Category:Class Method missing app/controllers/catalog_controller.rb:41:in `products_by_category'

What am I doing wrong? Would you recommend a better way of achieving this?

TIA, Elle

2 

Try this instead
38. def products_by_category
39. @category = Category.find(params[:id])
40. @page_title = @category.name
41. @products = @category.products
42. end

If you want them in a certain order, add :order to your has_many relationship.

elle wrote:

3

btw, you can also eliminate @products altogether and just use @category.products.each do |product| in your view.

William Pratt wrote:

4

btw, the reason that Category.products didn’t work is because the has_many association adds an instance method to the Category model, not a class method, so Category.products is not a method, but c = Category.find(:first); c.products is.

Hope this helps.

elle wrote:

5

Thanks William. The first solution didn't work. And when I try the second one like this:

<% if category.products? %> <p>No Products found for this category</p> <% else %> <ul id="products">   <% @category.products.each do |product| %>   <li><% product %></li>   <% end %> </ul> <% end %>

I get a NameError: undefined local variable or method `category' for #<#<Class:0x3260810>: 0x3260748> Extracted source (around line #1)...

Again, what am I doing wrong??

Thanks, Elle

6

You need the @ in front of category as it’s an instance variable…so it woud be

<% unless @category.products.empty? -%>

<p>No Products found for this category</p>

<% else %>

<ul id="products">

<% @category.products.each do |product| %>

    <li><% product %></li>

<% end %>

</ul>

<% end %>

elle wrote:

7

Sorry…my bad

<% if @category.products.empty? -%>

<p>No Products found for this category</p>

<% else %>

<ul id="products">

<% @category.products.each do |product| %>

    <li><% product %></li>

<% end %>

</ul>

<% end %>

William Pratt wrote:

8

I now get a 500 Internal Server Error. Would you know why? Elle

9

No, sorry. My mistake. I get: No products found for this category - even though I know for a fact that I do have products for the category.

10

It's hard to say without seeing your full controller method, and your category / product models and your database data. Try using script/console to play around with the relationships and debug it there.

Try: /script/console

then: c = Category.find(1) #(or whatever category id you are looking at now)

then: c.products

None-the-less, playing with it in script/console will help you narrow it down, and if it works as expected there, the problem must be in your controller and / or view code somewhere.

elle wrote:

11

It worked in the console. I changed it to this: <%= product.title %> and it worked. :))))

I then changed it to be a link: <%= link_to product.title, :action => "show", :id => product %>

Thank you so much :slight_smile: Elle

12

You *can* do that, but I don't advise it. I think the code is easier to deal with when all queries are executed in the controller, and all the view does is render things that the controller has set up. It certainly makes your code easier to test, since you can check assigns(:products) in the test method.

Could I ask (what might be a silly question) how would you run the query in the controller? and how would I change my code in my view?

Elle

13

just use the version that I submitted before the referenced post.

In the controller:

@products = @category.products

Then in the view:

<% @products.each do |product| -%>

#do stuff with product

<% end -%>

Josh Susser wrote: