= Features
Features is a nice little gem for associating application features with an active record model in a Rails app.

Developed and used on http://zendesk.com for account owners to switch different application features on and off.

== Sponsored by Zendesk - Enlightened Customer Support

== Description

If the feature set of your application grows, some customers would like to limit the features to only include what they
need. To enable your customers at Zendesk to customize their help desk to their needs, we developed this nice lille feature
management system, that we thought someone else out there might find useful.

You can define your feature set in a nice directly in the class that should be associated with features:

  class Account < ActiveRecord::Base
    has_features do
      feature :archive
      feature :ssl
    end
  end
  
Which would enable code like:

  account.features.archive? # checks weather an account has the archive feature.
  account.features.archive.create # adds the archive feature to the account
  account.features.archive.destroy # removes the archive feature to the account
  account.features?(:account, :ssl) # checks if the account has both the archive and ssl features

You can also define feature dependencies:

  class Account < ActiveRecord::Base
    has_features do
      feature :archive
      feature :premium
      feature :ssl, :requires => [:premium]
    end
  end

Which would enable code like:

  account.features.ssl.available? # returns true if all the required features of the ssl feature are met.
  account.features.ssl.create # raises a Features::RequirementsError if the account doesn't have the premium feature
  account.features.premium.destroy # would also destroy the ssl feature

Features can also be updated with the update_attributes and update_attributes! methods.
  
  #assuming params include { :account => { :features => { :archive => '1', :ssl => '0' } } }
  account.update_attributes(params[:account]) # would add the archive feature and remove the ssl feature
  
WARNING: You might want to protect some features from being updated with update_attributes. You can do this with:

  class Account < ActiveRecord::Base
    has_features do
      feature :archive
      feature :premium, :protected => true
      feature :ssl, :requires => [:premium]
    end
  end

This would protect the premium feature from being updated with update_attributes and update_attributes! The premium feature can only be updated with account.features.premium.create and account.features.premium.destroy.

We also created a view helper to help you generate the UI for enabling and disabling features:

  <% form_for(:account, :html => { :method => :put }) do |f| %>
    <h3>
      <%= f.feature_check_box :ssl %> Enable SSL on your account
    </h3>
  <% end %>

== Known issues

Let us know if you find any.

== Requirements

* ActiveRecord
* ActionPack

== LICENSE:

(The MIT License)

Copyright (c) 2009 Zendesk

Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following
conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.