#221 Subdomains in Rails 3

Jul 05, 2010 | 13 minutes | Routing, Rails 3.0

It is now possible to add subdomains to Rails 3 without the use of additional plugins. Learn how in this episode.

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Note: If you are using Rails 3.1 or later, be certain to check out revised episode 123.

          routes.rb
        
constraints(Subdomain) do
  match '/' => 'blogs#show'
end

          lib/subdomain.rb
        
class Subdomain
  def self.matches?(request)
    request.subdomain.present? && request.subdomain != "www"
  end
end

          app/helpers/url_helper.rb
        
module UrlHelper
  def with_subdomain(subdomain)
    subdomain = (subdomain || "")
    subdomain += "." unless subdomain.empty?
    [subdomain, request.domain, request.port_string].join
  end
  
  def url_for(options = nil)
    if options.kind_of?(Hash) && options.has_key?(:subdomain)
      options[:host] = with_subdomain(options.delete(:subdomain))
    end
    super
  end
end

          application_controller.rb
        
include UrlHelper

          config/initializers/session_store.rb
        
# requires Rails 3.0 RC or head
Rails.application.config.session_store :cookie_store, :key => '_blogs_session', :domain => :all

# change top level domain size
request.domain(2)
request.subdomain(2)
Rails.application.config.session_store :cookie_store, :key => '_blogs_session', :domain => "example.co.uk"

          blogs/index.html.erb
        
<%= link_to blog.name, root_url(:subdomain => blog.subdomain) %>

          blogs/show.html.erb
        
<%= link_to "All Blogs", root_url(:subdomain => false) %>