class RestrictIP
  def initialize(app, message = "Hello")
    @app = app
    @message = message
  end

  def call(env)
    dup._call(env)
    @ip = env['HTTP_X_REAL_IP'] ||= env['REMOTE_ADDR']
  end

  def each(&block)
    block.call("<!-- #{@ip} -->n")
    @response.each(&block)
  end
end

NoMethodError (You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.[]=):