user_class_extensions.rb

Spree::Core::Engine.config.to_prepare do
  if Spree.user_class
    Spree.user_class.class_eval do
      include Spree::Core::UserBanners
      has_and_belongs_to_many :spree_roles,
                              :join_table => 'spree_roles_users',
                              :foreign_key => "user_id",
                              :class_name => "Spree::Role"

      has_many :spree_orders, :foreign_key => "user_id", :class_name => "Spree::Order"

      # has_spree_role? simply needs to return true or false whether a user has a role or not.
      def has_spree_role?(role_in_question)
        spree_roles.any? { |role| role.name == role_in_question.to_s }
      end
    end
  end
end