rack middleware simple demo

app.rb

require 'sinatra/base'

class MyApp < Sinatra::Base
  get '/' do
    'top page'
  end
end

config.ru

require File.expand_path 'middleware', File.dirname(__FILE__)
use Middleware

require File.expand_path 'app', File.dirname(__FILE__)
run MyApp

middleware.rb

class Middleware
  def initialize(app)
    @app = app
  end

  def call(env)
    @app.call env
  end
end