class MyCell < Cell::Rails

  include CanCan::ControllerAdditions

end

如果你也在使用Devise,我必须这样做：

class MyCell < Cell::Rails

  include CanCan::ControllerAdditions
  include Devise::Controllers::Helpers
  Devise::Controllers::Helpers.define_helpers(Devise::Mapping.new(:user,{}))

end

#define_helpers会添加辅助方法,如current_user和user_signed_in？到细胞.