Automatically prepending url’s with http://

Recently we added functionality that allowed users to include links to images that they uploaded to one of our sites. In order to make the experience as easy as possible for users we allowed them to enter the url with or without the protocol (http:// or https://).

In order to make sure that any of our models that stored the information would always return a link with the protocol in it I wanted to create a simple mixin that would override the existing link method returned from the database and prepend http:// to it if it needed to.

Checking for the protocol and inserting it
This is actually quite a simple method. The following code was used to override the source_url method that was returning the link from the database.

def source_url
  link = super
  "#{link.match(/(http|https):\/\//i) ? '' : 'http://'}#{link}"

Since I was going to add this to a number of models it made sense to convert this to a mixin that could be used on any of the modules.

module Protocolize
  def self.included(klass)
    klass.class_eval do
      def self.protocolize(link_method)
        define_method link_method.to_sym do
          link = super()
          return nil if link.blank?
          "#{link.match(/(http|https):\/\//i) ? '' : 'http://'}#{link}"

This can then be called using the following in your model:

include Protocolize
protocolize :method_name

Notice that you have to explicitly call super() with params and not just super when you use it within define_method. If you don’t you will get the following error:

implicit argument passing of super from method defined by define_method() is not supported. Specify all arguments explicitly.

Just a tiny snippet that might be useful to people to ensure their links work correctly.


Rails 3, Rake and url_for

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] = ''
  url = url_for(:controller => 'foo', :action => 'bar')

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


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] = ''
  url = url_for(post)

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