well, from what I can gather, there are two reasons that this isn’t working for you.

1. For the Reloader to work, you need to have the code that needs to be reloaded to be in a separate file. So just move HelloWorld to hello_world.rb

2. At the end of Rack::Builder.new, add the to_app() method.

app = Rack::Builder.new do
use Rack::CommonLogger
use Rack::ShowExceptions
use Rack::Reloader
use Rack::ShowStatus
use Rack::Lint
run HelloWorld.new
end.to_app

I discovered this through the “mailing list”:http://groups.google.com/group/rack-devel/browse_thread/thread/11681e8ce6b58cac

================================================
%w{rubygems rack thin}.each {|dep| require dep}

class HelloWorld
def call(env)
[200,{"Content-Type" => "text/html"},"hello world!!"]
end
end

app = Rack::Builder.new do
use Rack::CommonLogger
use Rack::ShowExceptions
use Rack::Reloader
use Rack::ShowStatus
use Rack::Lint
run HelloWorld.new
end

Rack::Handler::Thin.run(app, :Port => 3000)

============================================

if i change the “hello world!!!” string to something else. A refresh on the web browser doesnt works. I wonder am i missing something?