The problem

I’m doing rails development on and off for about 8 years now. And to be honest I often struggle to remember what is the url helper for such route:

resources :users do
  resources :posts do
    resources :tags do
      member do
        put :foo
      end
    end
  end
end

If I want to route to the foo action of the tags_controller scoped under posts and users, is it:

foo_users_posts_tag_path(params[:user_id], params[:post_id], params[:id])

or is it this:

users_posts_tag_foo_path(params[:user_id], params[:post_id], params[:id])

In such situation I have to resort to running rake routes.

The solution

With use of ActionDispatch::Routing::UrlFor#url_for I can write a generic helper that decodes the common rails nomenclature of the controller’s actions (ie. "users#index" as for index action of users controller).

class ApplicationController < ActionController::Base
  helper_method :url_for!

  def url_for!(name, parameters = {})
    controller, action = name.split("#")
    url_for({controller: "/#{controller}", action: action}.merge(parameters))
  end
end

# and in the view or other controller

url_for!("tags#foo",
         user_id:   params[:user_id],
         post_id:   params[:post_id],
         id:        params[:id],
         any_other: "optional param")

Maybe it’s a bit more to write, but it’s far simpler to use.