Customized URLs in Rails with to_param

This is probably one of the most basic concepts for experienced Rails developers, but I had a hard time finding what I was looking for on Google, which means that other people are having a hard time too, so here's my first little contribution to the Rails community…

I recently moved from SubText to a tiny little (incomplete!) blog engine that I wrote for myself in Rails. While working on it, I was also reading a little bit about SEO; one of the concepts expressed was that each url on your site should have something to do with the content of the page to which it refers. While Rails has good defaults for a lot of things, a url like http://example.com/posts/123 certainly leaves room for improvement.

While I knew that I could accomplish the affect that I wanted by creating a bunch of custom routes in routes.rb, I wanted to be able to take advantage of map.resource and methods such as link_to, which seemed to insist upon using the record ID of my ActiveRecord model.

Until I found to_param.

to_param, as it turns out, is a very simple method that you can override in any ActiveRecord model. Whatever value you return from this method will be used in any urls generated by methods like link_to. The one caveat is that after you do this, you must change the code for any of your controllers so that they look up records based on this new external ID. In many cases, this may be as simple as changing MyController.find(params[:id]) to MyController.find_by_name(params[:id]).