Map classes to sinatra routes

app.rb

require 'rubygems'
require 'sinatra'

class Handler
  attr_reader :context
  def initialize(context)
    @context = context
  end
  def render
    unless context.params[:username].nil?
      "Hello #{context.params[:username]}"
    else
      "Hello guest"
    end
  end
end

def Handler
  klass = Handler
  Proc.new do
    klass.new(self).render
  end
end

get "/", &Handler()
get "/:username", &Handler()