FriendlyId

FriendlyId is the “Swiss Army bulldozer” of slugging and permalink plugins for Ruby on Rails. It allows you to create pretty URL’s and work with human-friendly strings as if they were numeric ids for ActiveRecord models.

Using FriendlyId, it’s easy to make your application use URL’s like:

http://example.com/states/washington

instead of:

http://example.com/states/4323454

Want to find out more? Read on. The most recent version of the FriendlyId RDocs can always be found on Rubyforge.

Why?

Text-based id’s look better
They make URL’s easier to remember.
They give no hint about the number of records in your database.
They are better for search engine optimization.

But…

They can change, breaking your URL’s and your SEO.
It can be tricky to ensure they’re always unique.
They can become a pain to manage in large Rails applications.
They can conflict with your application’s namespace.

FriendlyId tries to offer you the all the advantages, and avoid or soften the potential impact of the disadvantages.

Typical Uses

User names (“non-slugged” models)

Usually users have unique user names stored in a column with a unique constraint or index. In this case, all you need to do is add this to your model:

has_friendly_id :login

and you can then write code like this:

@member = Member.find("joe")   # the old Member.find(1) still works, too.
@member.to_param               # returns "joe"
redirect_to @member            # The URL would be /members/joe

Blog posts (“slugged” models)

Blog posts generally have titles which are distinctive but not necessarily unique. In this and similar cases, FriendlyId provides a Slug model separate from your Post model. The Slug model handles duplicate friendly_ids, as well as versioning.

Your model code would look something like this:

has_friendly_id :title, :use_slug => true

and you can then write code like this:

@post = Post.find("new-version-released")  # Post.find(1) still works, too
@post.to_param                             # returns "new-version-released"
redirect_to @post                          # The URL would be /posts/new-version-released

Now in your controllers, if you want to prevent people from accessing your models by numeric id, you can detect whether they were found by the friendly_id:

@post = Post.find(params[:id])
raise "some error" if !@post.found_using_friendly_id?

or, you can 301 redirect if the model was found by the numeric id if you don’t care about numeric access, but want the SEO value of the friendly_id:

@post = Post.find(params[:id])
redirect_to @post, :status => 301 if @post.has_better_id?

The “has_better_id?” method returns true if the model was found with the numeric id, or with an outdated slug.

Extra Features

Slug Versioning

FriendlyId will record changes to slugs so that you can tell when the model is found with an older slug, or by the numeric id. This can be useful if you want to do a 301 redirect to your updated URL.

class PostsController < ApplicationController

  before_filter ensure_current_post_url, :only => :show

  ...

  def ensure_current_post_url
    redirect_to @post, :status => :moved_permanently if @post.has_better_id?
  end

end

This is particularly useful when implementing FrindlyId on an existing website that already has many URL’s with the old numeric id listed on search engines. When the search engine spiders crawl your site, they will eventually pick up the new, more SEO-friendly URL’s.

Non-unique Slug Names

FriendlyId will append a arbitrary number to the end of the id to keep it unique if necessary:

/posts/new-version-released
/posts/new-version-released--2
/posts/new-version-released--3
...
etc.

Note that the number is preceeded by two dashes to distinguish it from the rest of the slug. This is important to enable having slugs like:

/cars/peugeot-206
/cars/peugeot-206--2

Reserved Names

You can mark off some strings as reserved so that, for example, you don’t end up with this problem:

/users/joe-schmoe # A user chose "joe schmoe" as his user name - no worries.
/users/new # A user chose "new" as his user name, and now no one can sign up.

Here’s how to do it:

class Restaurant < ActiveRecord::Base
  belongs_to :city
  has_friendly_id :name, :use_slug => true, :reserved => ["my", "values"]
end

As of FriendlyId version 2.0.2, “new” and “index” are reseved by default. When you attempt to store a reserved value, FriendlyId raises a FriendlyId::SlugGenerationError.

Scoped Slugs

FriendlyId can generate unique slugs within a given scope. For example:

class Restaurant < ActiveRecord::Base
  belongs_to :city
  has_friendly_id :name, :use_slug => true, :scope => :city
end

class City < ActiveRecord::Base
  has_many :restaurants
  has_friendly_id :name, :use_slug => true
end

http://example.org/cities/seattle/restaurants/joes-diner
http://example.org/cities/chicago/restaurants/joes-diner

Restaurant.find("joes-diner", :scope => "seattle") # returns 1 record
Restaurant.find("joes-diner", :scope => "chicago") # returns 1 record
Restaurant.find("joes-diner") # returns both records

The value for the :scope key in your model can be a custom method you define, or the name of a relation. If it’s the name of a relation, then the scope’s text value will be the result of calling to_param on the related model record. In the example above, the city model also uses FriendlyId and so its to_param method returns its friendly_id: chicago or seattle.

This feature is new in FriendlyId 2 and should be considered of experimental quality. Please don’t use this for code that needs to run on the Space Shuttle.

Text Normalization

FriendlyId’s slugging can strip diacritics from Western European characters, so that you can have ASCII-only URL’s; for example, conveting “ñøîéçü” to “noiecu.”

has_friendly_id :title, :use_slug => true, :strip_diacritics => true

If you are not using slugs, you’ll have to do this manually for whatever value you’re using as the friendly_id.

Diacritic-sensitive normalization

FriendlyId can also normalize slug text while preserving accented characters, if you prefer to leave them in your URL’s:

has_friendly_id :title, :use_slug => true
...
@post = Post.create(:title => "¡Feliz Año!")
@post.friendly_id # "feliz-año"

Unicode URL’s

FriendlyId can generate slugs in any language that can be written with Unicode. It does its best to strip away punctuation regardless of the language being used. Since the authors only speak English, Spanish, Portuguese and German, this has not been extensively tested with anything like Chinese, Russian, Greek, etc, but it “should work.” If you’re a speaker of a language that uses a non-Roman writing system, your feedback would be most welcome.

has_friendly_id :title, :use_slug => true
...
@post = Post.create(:title => "友好编号在中国")
@post.friendly_id # "友好编号在中国"
@post2 = Post.create(:title => "友好编号在中国")
@post2.friendly_id # "友好编号在中国--2"

Custom Slug Generation

While FriendlyId’s slug generation options work for most people, you may need something else. As of version 2.0.4 you can pass in your own custom slug generation block:

class Post < ActiveRecord::Base
  has_friendly_id :title, :use_slug => true do |text|
    MySlugGeneratorClass::my_slug_method(text)
  end
end

FriendlyId will still respect your settings for max length and reserved words, but will use your block rather than the baked-in methods to normalize the friendly_id text.

Getting it

FriendlyId is best installed as a Ruby Gem:

gem install friendly_id

Alternatively, you can install it as a Rails plugin, though this is discouraged:

./script/plugin install git://github.com/norman/friendly_id.git

Setting it up

The current release works with Rails 2.2 and above, and is compatible with Ruby 1.8 and 1.9. If you need support for Rails 2.0 - 2.1, you need to install an older version of FriendlyId. Here’s how to set it up.

1) Install the Gem:

sudo gem install friendly_id
cd my_app
script/generate friendly_id
rake db:migrate

2) Load FriendlyId in your app:

# Rails 2.1 and higher; add this to the gem section of environment.rb:
config.gem "friendly_id"

# Rails 2.0; this goes at the bottom of environment.rb
require 'friendly_id'

3) Add some code to your models:

class Post < ActiveRecord::Base
  has_friendly_id :title, :use_slug => true
end

4) If you are using slugs, you can use a Rake task to generate slugs for your existing records:

friendly_id:make_slugs MODEL=MyModelName

If you eventually want to expire old slugs every so often, or perhaps every day via cron, you can do:

rake:friendly_id:remove_old_slugs

The default is to remove dead slugs older than 45 days, but is configurable:

rake:friendly_id:remove_old_slugs MODEL=MyModelName DAYS=60

Installing an older version

If you are still on Rails 2.1 or lower, please install version 2.0.4:

gem install friendly_id –version 2.0.4

Note that this version depends on the Unicode gem, which doesn’t compile on Windows and is incompatible with Ruby 1.9. It also can’t be installed on Heroku. If these are problems, you’ll need to update your application to Rails 2.2 or higher and use the current release of FriendlyId.

Upgrading from an older version

If you installed an older version of FriendlyId and want to upgrade to 2.0.x, follow these steps:

Install the friendly_id Gem:

sudo gem install friendly_id

Add FriendlyId to environment.rb:

For Rails 2.1 and higher:

config.gem "friendly_id"

For Rails 2.0:

Add this to the bottom of environment.rb:

require 'friendly_id'

Remove the older version of FriendlyId:

git rm -rf vendor/plugins/friendly_id
svn delete vendor/plugins/friendly_id
# or whatever

Generate the upgrade migration and run it

./script generate friendly_id_20_upgrade
rake db:migrate

Hacking FriendlyId:

FriendlyId is hosted on Github, and we love pull requests. :-)

Bugs:

Please report them on Lighthouse.

Credits:

FriendlyId was created by Norman Clarke, Adrian Mugnolo, and Emilio Tagua.