Before I start I just want to make it clear that I know the arguments against using url_for in models and even in rake tasks. Sometimes however it makes sense to use_url for in a rake task. In my case I am trying to query another site’s api which requires the URI of the page on my site that I want to gather information about.

The approach in Rails 2.x

task :collect_stats => :environment do
  include ActionController::UrlWriter

  default_url_options[:host] = 'www.example.com'
  url = url_for(:controller => 'foo', :action => 'bar')
end

Notice that because there is no current request you have to specify the

default_url_options[:host]

as the helper has no idea what the host will be otherwise.

Doing the same thing in Rails 3

The following code does the same thing in Rails 3.

task :collect_stats => :environment do
  include ActionDispatch::Routing::UrlFor
  #include ActionController::UrlFor  #requires a request object
  include ActionController::PolymorphicRoutes
  include Rails.application.routes.url_helpers

  default_url_options[:host] = 'www.example.com'
  url = url_for(post)
end

There are two key points to notice here.

1. The first is that I have included ActionDispatch::Routing::UrlFor rather than ActionController::UrlFor. The latter requires a request object and will attempt to automatically fill in the host name. Since we are in a rake task there is no request and the method will fail.
2. The second thing is that I have also included two additional includes. The will allow you to work with polymorphic routes and named routes, giving a bit more flexibility.

Just a short snippet that might be of use to people but if there are any improvements out there then please let me know and I will update this. You can of course hard code the routes but there are scenarios where it makes much more sense to make use of the helpers provided, especially when using polymorphic routes.

Update: 08/06/2010

In the comments Jakub has stated that in the latest version of Rails you don’t need to include the polymorphic routes.

include ActionController::PolymorphicRoutes