flash.rb

# Originally from 
# http://github.com/i2av/sinatra-flash/blob/7bb1f5e0a1093d4f114bbe8074bb1a7792bc5ab1/app.rb
# but heavily modified

module Sinatra
  module Flash
    module RedirectHelper
      def redirect(uri, *args)
        session[:_flash] = flash unless flash.empty?
        status 302
        response['Location'] = uri
        halt(*args)
      end
    end
  
    module FlashHelper
      def flash
        @_flash ||= {}
      end
    end
  
    def self.registered(app)
      app.helpers RedirectHelper
      app.helpers FlashHelper
      app.enable :sessions
    
      app.before do
        @_flash, session[:_flash] = session[:_flash], nil if session[:_flash]
      end
    end
  end
  
  register Flash
end