Railscasts - Subdomains in Rails 3

#221

Jul 05, 2010

45 comments

Subdomains in Rails 3

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

Tags: routing rails-3.0

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Resources

# 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) %>

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45 comments

1. Золзаяа Jul 05, 2010 at 01:27

Thanks for this post.

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2. docgecko Jul 05, 2010 at 02:23

Thanks for this Ryan!

I've been trying to get Devise and subdomains to work together, by using one of the Subdomain plugins, but not managed to get there fully. Going to have a go using your approach now and see how I get on.

Keep up the great casts, they are always mega helpful!

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3. jim Jul 05, 2010 at 03:32

Great post Ryan! Thanks!

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4. tomekw Jul 05, 2010 at 05:03

There is a typo in "http://github.com/ryanb/railcasts-episodes/tree/master/episode-221" link: it should be "http://github.com/ryanb/railscasts-episodes/tree/master/episode-221" (missing "s" in railscasts-episodes".

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5. Marcelo Silveira Jul 05, 2010 at 06:41

Great, thanks!

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6. Wade West Jul 05, 2010 at 07:41

Another great screencast Ryan. Thank You. And as a side note, today's my birthday :)

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7. Emerson Lackey Jul 05, 2010 at 08:54

Finally got Rails 3 working with RVM. Stopped using my local Passenger installation and now I'm really enjoying the flexibility of jumping around to different versions of Ruby/Rails.

Currently developing an app that requires account level subdomains and was unhappy with the options in Rails 2.3...

Looking forward to Rails 3 RC, thanks again for all the awesome screencasts!

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8. Jaime Jul 05, 2010 at 09:03

Cool tricks, Ryan.

You just gave me some ideas to try out on my pet projects :)

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9. Ryan Bates Jul 05, 2010 at 09:35

@tomekw, thanks, fixed!

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10. dotemacs Jul 05, 2010 at 09:55

Great vid, was meaning to have a look at the subdomains in rails3, but you just summed it up nicely.

Also plus points for picking up on smackaho.st :)

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11. dhc Jul 05, 2010 at 11:26

In this line of your code:

options[:host] = with_subdomain(options.delete(:subdomain))

what does options.delete() do? It doesn't seem intuitive, which is rare in Ruby.

--dhc

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12. Alexander Jul 05, 2010 at 12:14

Is it possible to use domain size 0? I need to show different content depending on domain name, but the main part of the site is the same.

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13. Gigamo Jul 05, 2010 at 14:47

@dhc: It removes the passed element from the hash and returns it. See http://ruby-doc.org/core/classes/Hash.html#M002870

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14. bluecoda Jul 05, 2010 at 20:07

Very great episode. i've been waiting this for a long time.Thank you very much~Very good job

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15. Alexey Poimtsev Jul 06, 2010 at 00:45

Hi, Ryan.
I've wrote similar article some months ago (http://bit.ly/ajGym2 - sorry, only Russian version, but you can use Google Translate) but there are some problems with session sharing between subdomains in Opera browser - unfortunately Opera cannot read cookies from sibling domain - it means if you set cookie for dom1.example.com cookie cannot be read from dom2.example.com

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16. Frederic Jul 06, 2010 at 03:20

@Alexey Poimtsev:

There's a blog article on my.opera.com that describes how the Opera browser deals with cookie sharing between subdomains.

To sumarize (very quickly) the article: any *.example.tld subdomains are considered as siblings (and can share domain=.example.tld cookies) if the example.tld domain has a registered IP address in DNS.

The reality is a little more complicated, so the
http://my.opera.com/yngve/blog/show.dml/267415 article deserves a reading.

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17. davidrv Jul 06, 2010 at 04:38

Nice! Thx :)

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18. Bagwan Pankaj Jul 06, 2010 at 06:12

Nice post. Thanks

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19. Jamie Hill Jul 06, 2010 at 07:00

Thanks Ryan!

I really wish I had this to hand a couple of weeks ago when trying to figure out the subdomain stuff in Rails 3. This has helped me to tidy up my code somewhat.

I'd really like to see the ":subdomain" option on url helpers as a patch for Rails 3, will you be submitting? ...If not I may do so as it's super useful.

Thanks again.

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20. Ryan Bates Jul 06, 2010 at 10:40

@Alexander, I mention changing the top level domain size at the end of the episode. I haven't tested it, but passing "0" for the tld size should work.

@Jamie, I think the problem with adding a built-in :subdomain option is that the top level domain size is not easily configurable.

That said, I think a ticket on configuring the default tld size along with this would be great. I don't have plans to do this so feel free to.

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21. Mario Uher Jul 07, 2010 at 00:01

I think

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

can be even shorter, like

constraints(Subdomain) do
root :to => 'blogs#show'
end

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22. Roland Jul 08, 2010 at 04:56

If you have to deal with various top level domains and third level assignments in parallel (.e.g. some have .com, some others co.uk) you may want to use the public suffix library from:

http://www.simonecarletti.com/blog/2010/06/public-suffix-list-library-for-ruby/

This is far better than hardcoding the length in your app and also used by browser vendors already.

hth,
Roland

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23. wout fierens Jul 08, 2010 at 10:45

You made my day Ryan! Thanks to you I moved a rather complex Rails app with various subdomain implementations from 2.3.8 to 3 in less than a day.

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24. Matt Beedle Jul 09, 2010 at 11:12

I just figured out how to get this working and blogged about it a couple of days before you did this! I like your solution more though. In case anyone is interested, I also blogged about how to test it with cucumber/capybara: http://mattbeedle.com/2010/07/04/testing-subdomains-with-cucumber-cabybara-and-rack-test

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25. Steve Jul 10, 2010 at 09:17

I just get an error...

uninitialized constant Subdomain (NameError)

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26. Samuel Lebeau Jul 12, 2010 at 06:48

Great screencast as usual, thanks Ryan !

On Mac OS X, "*.127localhost.*" resolves to 127.0.0.1 too: it's really helpful to test applications against both subdomains and TLDs.

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Thanks for this post, but it don't work for ActionMailer.

Here my path:
http://gist.github.com/478169

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35. George Ornbo Aug 01, 2010 at 05:49

If you get the error

uninitialized constant Subdomain (NameError)

it seems that in the later versions of the Rails 3 beta or the edge version the routes file doesn't autoload /lib/subdomain.rb

Adding

require 'subdomain'

before the routes block fixes this.

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or the edge version the routes file doesn't autoload /lib/subdomain.rb

Adding

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In Rails 3.0.0.rc there seems to be an issue using :domain => :all - it flips out with an InvalidAuthenticityToken error. Using :domain => ".smackaho.st" works for the time being.

Per https://rails.lighthouseapp.com/projects/8994/tickets/5147-the-all-domain-option-for-the-cookie-session-store-doesnt-allow-non-standard-tlds-like-local-or-couk

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@george (#35) : I agree.

It's weird that in the session_store.rb file, :domain => :all doesn't work for me (in Edge). :domain => 'lvh.me' does work though... any insights about this?

@docgecko (#2) : devise works fine for me here.

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49. Daniel Kehoe Aug 17, 2010 at 15:13

@Doug Mayer (#36):
@thb (#47):

:domain => :all doesn't work in the Rails 3 release candidate (it results in an InvalidAuthenticityToken error). The issue is resolved in Rails 3 master on GitHub with commit fd78bb72704554737117 by Bryce Thornton on 14 Aug 2010.

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Thanks, Ryan! For anyone who needs more, I put together a Rails 3 example app (with a detailed walk-through tutorial) that shows how to set up subdomains in Rails 3 using Devise for authentication: http://github.com/fortuity/rails3-subdomain-devise (click above for the link). For anyone who needs a quick start for blog-style subdomains using Rails 3.

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Subdomains in Rails 3

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