lib/generators/active_record/templates/model.rb
has_and_belongs_to_many :<%= user_class.table_name %>, :join_table => :<%= join_table %>
<% if Rails::VERSION::MAJOR < 5 %>
belongs_to :resource,
:polymorphic => true
<% else %>
belongs_to :resource,
:polymorphic => true,
:optional => true
<% end %>
validates :resource_type,
:inclusion => { :in => Rolify.resource_types },
:allow_nil => true
scopify