Rack Middleware that implements Session Flash messages. (session values that will be available just for the request) Usage: use Rack::Session::Flash

gistfile1.rb

module Rack
  module Session
    class Flash
      def initialize(app)
        @app = app
      end

      def call(env)
        dup.call!(env)
      end

      def call!(env)
        env['rack.session'] || raise(RuntimeError,
          'You\'re missing a session handler. ' +
          'You can get started using Rack::Session::Cookie')

        env['rack.session']['flash'] ||= {}

        response = @app.call(env)

        env['rack.session']['flash'].clear

        response
      end
    end
  end
end