How to get url_helper to pass permalink instead of id in Rails?

Question

I have the following route in my Rails3 project:

match "/blog/:permalink" => "posts#show", :as => :post

When I link to my post through a view as such:

<%= link_to @post.title, post_path(@post) %>

The id of the post is passed into the post_path helper (even though my route specifies the permalink is passed.

How do I force the post_path to send in the permalink instead of the id of the post? I can explicitly call post_path(@post.permalink) but that seems dirty.

Am I missing something in my route?

Thanks!

Answer 1

Define a to_param method on the model that returns the string you want to use.

class Post < ActiveRecord::Base
  def to_param
    permalink
  end
end

See this page, this Railscast, (and of course Google) for more info.

[Edit]

I don't think Polymorphic URL Helpers are smart enough to handle what you want to do here. I think you have two options.

1. Use a special named route and pass in the parameter similar to your question and Jits' answer.

match "/blog/:permalink" => "posts#show", :as => :post

and link to it

<%= link_to @post.title, post_path(:permalink => @post.permalink) %>

2. Create a new helper that generates the URL for you

match "/blog/:permalink" => "posts#show", :as => :post_permalink

and a helper

def permalink_to(post)
  post_permalink_path(post.permalink)
end

and in your views

<%= link_to @post.title, permalink_to(@post) %>