ActionController::RecordIdentifier

The record identifier encapsulates a number of naming conventions for dealing with records, like Active Records or Active <a href="/rails/ActionController/Resources">Resources</a> or pretty much any other model type that has an id. These patterns are then used to try elevate the view actions to a higher logical level. Example:

  # routes
  map.resources :posts

  # view
  <% div_for(post) do %>     <div id="post_45" class="post">
    <%= post.body %>           What a wonderful world!
  <% end %>                  </div>

  # controller
  def destroy
    post = Post.find(params[:id])
    post.destroy

    respond_to do |format|
      format.html { redirect_to(post) } # Calls polymorphic_url(post) which in turn calls post_url(post)
      format.js do
        # Calls: new Effect.fade('post_45');
        render(:update) { |page| page[post].visual_effect(:fade) }
      end
    end
  end

As the example above shows, you can stop caring to a large extent what the actual id of the post is. You just know that one is being assigned and that the subsequent calls in redirect_to and the RJS expect that same naming convention and allows you to write less code if you follow it.