Question

i am returning to an application I wrote a few months ago and trying to make a few minor adjustments. I currently have a model Product and a catalogue page where all products are listed using an each loop for all entries in Product.

In order to attempt to keep the site secure I have put http://.../products/... behind a authentication login, so only users with a password can see /products/index, edit the product details and also see the products one at a time (show page).

I would now like to link from the page with all products listed to a page with just ONE product’s details (i.e. an individual product’s own page).

I am aware that I can find a product from the Product model using a find function for a Product ID, however, how do I go about automatically creating a sensible URL for this product’s listing?

In summary, if I had a listing of 10 products on a page, what is the best way of enabling a user to click on the product and be routed to a page called http://..../shop/specific_products_name? I have read around a bit and it appears to_param may be of some benefit, but I am struggling to work out a sensible means of creating these pages

Thanks for your time

Answer 1

Here’s a basic, conventional controller setup:

First, here’s the route shortcut syntax:

# config/routes.rb
...
resources :products
...

Here’s the controller that loads all the Products on the index and just one Product on the show.

# app/controllers/products_controller.rb
class ProductsController 
  def index
    @products = Product.all
  end

  def show
    @product = Product.find(params[:id])
  end   
end

That line in the routes file gives us these routes (among others):

• /products goes to products_controller#index
• /products/:id goes to products_controller#show with params[:id] set to the given number

The easiest way to get a pretty URL with the least amount of work is to, as you looked into, override to_param.

to_param is what Rails uses to turn a model into a representation in a url/request.

By default, it’s this:

class Product
  def to_param
    self.id
  end
end

So when Rails does a Product.find() on the result of that to_param, find() turns it into an integer with to_i.

If params[:id] is "24", then Product.find(params[:id]) converts “24” to the integer 24.

But consider how to_i works with other examples:

"100".to_i                     #=> 100
"100-flux-capacitor-2000".to_i #=> 100

In other words, if our parameter representation of a Product is "#{id}-the-product-name", Product.find(params[:id]) will still work even though our products#show URLs look like /products/56-ford-taurus.

One more thing:

"I love the Ford Taurus".parameterize #=> "i-love-the-ford-taurus"

Solution A

The easiest solution to your problem is to override to_param like this:

class Product
  def to_param
    "#{id}-#{name.parameterize}"
  end
end

The benefit of this method is that you change one method in the Product model and the rest of your code Just Works.

The downside is that your URLs looks like:

/products/56-ford-taurus

Instead of:

/products/ford-taurus

Solution B

If you want the latter example, you can maintain a slug column in the Products table.

Example:

Product
  id: 58
  name: Ford Taurus
  slug: ford-taurus

Then you could override to_param like this:

class Product
  def to_param
    slug
  end
end

Now, params[:id] would look like “ford-taurus”.

Product.find("ford-taurus") wouldn’t work anymore since find() wants an integer, so you could replace Product.find(params[:id]) with Product.find_by_slug(params[:id]).

You’d just have to make sure every product has a unique slug.

And you can automate the slug creation process with something like:

class Product
  before_create :make_slug

  private
  def make_slug
    self.slug = name.parameterize
  end
end

That way, you just need to set the product’s name on creation, save it, and its slug will become a URL friendly “whatever-the-product-name-was”.

• Plus side: Your URLs now only contain the product name with no ugly product ID.
• Down side: Changing the slug a product will break URLs, which is why my before_filter example only sets the slug on creation and not any time you save the product.

Now that Rails will generate the kind of URLs you want, you can generate links to these products in a view like this:

# This would be in views/index.html.erb
<% @products.each do |product| %>
  <%= link_to product.name, product %>
<% end %>

Would product this sort of html for each product:

<a href="/products/56-ford-taurus">Ford Taurus</a> (if you used Solution A)
<a href="/products/ford-taurus">Ford Taurus</a> (if you used Solution B)