flash

# File actionpack/lib/action_controller/flash.rb, line 148
        def flash(refresh = false) #:doc:
          if !defined?(@_flash) || refresh
            @_flash =
              if session.is_a?(Hash)
                # don't put flash in session if disabled
                FlashHash.new
              else
                # otherwise, session is a CGI::Session or a TestSession
                # so make sure it gets retrieved from/saved to session storage after request processing
                session["flash"] ||= FlashHash.new
              end
          end

          @_flash
        end