DataMapper

CanCan 1.5 adds support for DataMapper. All you have to do is mention dm-core before cancan in your Gemfile so it is required first.

gem "dm-core"
gem "cancan"

That is it, you can now call accessible_by on any DataMapper model (which is done automatically in the index action). You can also use the query syntax that DataMapper provides when defining the abilities.

# in Ability
can :read, Article, :priority.lt => 5
cannot :manage, Article, :priority.gte => 5

This is all done through a Model Adapter. See that page for more information and how you can add your own.