Alternative for CanCan?

For the same reason i've done this: http://mcasimir.github.com/checkin/.

Checkin is an authorization gem that is independent from the role/authentication library you use.

You can express even complex rules rather simply with a declarative/cascading permissions DSL.

I found it very handy. The debug is also supported via the explain method that will log the authorization process on every request.

Here are some of the features:

• Handy DSL to define roles and permissions with a declarative approach
• Check authorization for CRUD operations automatically
• Standard way to rescue from Authorization errors
• Authorization subject decoupled from model (compatible with any autentication system)
• Role-based authorization decoupled from role system (compatible with any role system)
• Decorator for current_user and other subject objects
• Scoped authorization rules
• Cascading authorization rules
• Simple: even complex authorization behaviour is understandable at glimpse and easily predictable
• Support for controller based mass assignment protection

Here is a very simple example of the DSL:

class UserSubject < Checkin::Subject

      role :guest, :alias => :anonymous do
          !subject_model
      end

      role :logged_in, :alias => [:connected] do
          !!subject_model
      end

      role :owner, :require => [:logged_in], :method => :own do |object|
          object && ( object.respond_to?(:author) && ( subject_model == object.author ) ) ||  ( object.respond_to?(:owner) && ( subject_model == object.owner ) )
      end

      role :administrator, :require => :logged_in, :alias => :admin do
          subject_model.has_role?(:administrator)
      end

      #
      # Permissions