From: Sys Ppp <systemppp@...>
Date: 2009-08-27T12:48:15+09:00
Subject: Re: Rack must not dictate how to create a middleware

Brian Candler wrote:

> I did look at this myself once - I wanted to be able to pass extra 
> parameters to the middleware modules. But the problem was the deferred 
> initialisation of the modules, which was required to build them in the 
> inside-out order. I decided that it was simpler in such cases not to use 
> middleware, but to construct the stack explicitly:
> 
>   run Foo.new(Bar.new(Baz.new))

It is not very hard.

module Node

  def create app
    @app = app
    self
  end

  def call env, *args
    str, *new_args = get_str args
    status, header, resp = @app.call env, new_args
    new_resp = Rack::Response.new(str, status, header)
    new_resp.write resp.body
    return new_resp.finish
  end

end

builder = Rack::Builder.new do
  use ...
  .......
  use ...

  map '/' do

    module MidA
      def self.get_str *args
        ["<p>MidA args: #{args}</p>\n", args, 'AAA']
      end
      extend Node
    end
    run MidA.method(:create)

    module MidB
      def self.get_str *args
        ["<p>MidB args: #{args}</p>\n", args, 'BBB']
      end
      extend Node
    end
    run MidB.method(:create)

    p = Proc.new do |env, *args|
      resp = Rack::Response.new
      resp.write "<p>Main args: #{args}</p>\n"
      resp.finish
    end
    run p

  end

end

Or something else like that.

I think, blocks may be easy passed down to middleware chains. Like this.
status, header, resp = @app.call env, args {|...| ...}
But I have not yet invented how to use such pervertion. :)
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