PerActionMw -- Per Action Middleware for Action Controller
===========

This experimental plugin lets you add Rack middleware on a per-controller,
per-action basis. It is used somewhat in the before/after_filter style, but
is in the spirit of the middleware stack handlers. 

The idea is to bring the benefit of Rack-style middleware down to the controller
action level of granularity. 


Example
=======

Here's a complete, albeit dinky, example:

  # Create a Rack app. @app will be set for you. You can
  # also write your own initialize method if you wish. 

    class MyRackApp
      def call(env)

    # Do stuff before request is handled
        env["X-David"] = "Black"

    # Handle request
        status, headers, response = @app.call(env)

    # Do stuff after request is handled and forward response
        response.body.gsub!(/Dave/, "David")
        response.to_a
      end
    end


  # In your controller, call the "middle" class method, which
  # takes an app class name as its argument and also takes
  # the :only and :except parameters (via hash keys)

    class ThingsController < ApplicationController
      middle MyRackApp, :only => "show"
  
      def index
        @things = Thing.find(:all)
      end

      def show
        if request.headers["X-David"] == "Black"
          logger.info("Header got set!")
        end
    
        @thing = Thing.find(params[:id])
      end
    end

Your view will be rendered with Dave changed to David throughout. 

How it works
============

The plugin modifies the ActionController#process method, so that it is
tied to a middleware stack, much as the ActionController::Dispatcher#dispatch
method is. When the request comes in, the middleware in the stack is triggered
"domino"-style, with the final piece of middleware making the call to the "real"
request handlers. 

The controller class keeps track of which actions (for that controller) use which
middleware, in the event that you use the :only and/or :except parameters. 


Author
======

David A. Black (dblack@rubypal.com)
January 16, 2009

Copyright (c) 2009 Ruby Power and Light, LLC, released under the MIT license