Question

Currently I have a route that looks like this:

resources :posts

I want to override the ‘show’ action so that I can display a url like this:

posts/:id/:slug

I am currently able to do this by adding a custom match route:

resources :posts
match 'posts/:id/:slug' => 'posts#show'

However, when I use the link_to helper, it does not use my custom show route.

<%= link_to 'show', post %>  # renders /posts/123

How can I define my show route so that I can still use the link_to helper?

Update: As you can read in the following answers, you can override the route to the ‘show’ action, but it’s probably more work than it’s worth. It’s easier to just create a custom route:

# config/routes.rb
match 'posts/:id/:slug' => 'posts#show', as: 'post_seo'

# app/views/posts/index.html.erb
<%= link_to post.title, post_seo_path(post.id, post.slug) %>

Answer 1

You have two routes which point to posts#show (you should be able to confirm this by running rake routes), and your link is using the wrong one.

When you call link_to('show', post) the URL of the link is generated by calling url_for(post) which (eventually, after passing through several other methods on the way) calls post_path(post). Since the route to posts#show that was created by your call to resources(:posts) is named post, that is the route that post_path generates.

You also currently have inconsistent routes for the show, update and destroy actions which will probably cause you problems later on.

You can fix this by changing your routes to the following:

resources :posts, :except => ['show', 'update', 'destroy']
get    'posts/:id/:slug' => 'posts#show', :as => 'post'
put    'posts/:id/:slug' => 'posts#update'
delete 'posts/:id/:slug' => 'posts#destroy'

Unfortunately you still can’t use link_to('show', post) just yet, because it relies on being able to use post.to_param as the single argument needed to build a path to a post. Your custom route requires two arguments, an id and a slug. So now your link code will need to look like this:

link_to 'show', post_path(post.id, post.slug)

You can get around that problem by defining your own post_path and post_url helpers in app/helpers/posts_helper.rb:

module PostsHelper
  def post_path(post, options={})
    post_url(post, options.merge(:only_path => true))
  end

  def post_url(post, options={})
    url_for(options.merge(:controller => 'posts', :action => 'show',
                          :id => post.id, :slug => post.slug))
  end
end

Which means we’re finally able to use:

link_to 'show', post

---

If that all seems like too much work, a common alternative is to use URLs that look more like posts/:id-:slug, in which case you can stick with the standard RESTful routes and just override the to_param method in your Post class:

def to_param
  "#{id}-#{slug}"
end

You’ll also need to do a little bit of work splitting up params[:id] into an ID and a slug before you can look up the relevant instance in your show, edit, update and destroy controller actions.