gistfile1.rb

class Ability
  include CanCan::Ability

  def initialize(user)
    can [:read, :sort], Feature do |feature|
      # below is turning into an idiom for me, one I sometimes forget about. 
      # thoughts on a better way to expose the "if we have an instance, use this check, else grant access to read/sort the Feature class"
      (feature && feature.project.has_user?(user)) || true
    end
  end
end