A basic RESTful Sinatra application

app.rb

require 'rubygems'
require 'erb'
require 'sinatra/base'

# A basic RESTful Sinatra app for serving some kind of object.  Uses views:
#
#   views
#   |- error.erb
#   |- index.erb
#   |- layout.erb
#   |- show.erb
#   `- unknown.erb
#
class App < Sinatra::Base
  set :root, File.expand_path(File.dirname(__FILE__) + "/..")
  set :raise_errors, false
  set :dump_errors, true
  template(:layout) do
    File.read("views/layout.erb")
  end
  error RuntimeError do
    erb :error, :locals => {:err => env['sinatra.error']}
  end

  get('/')    { index}
  get('/:id') {|id| show(id) }
  post('/')   { create(request[:id]) }
  post '/:id' do |id|
    _method = request[:_method]
    case _method
    when /\Aupdate\z/i then update(id)
    when /\Adelete\z/i then destroy(id)
    when nil           then create(id)
    else error("unknown post method: #{_method}")
    end
  end
  put('/:id')    {|id| update(id) }
  delete('/:id') {|id| destroy(id) }

  attr_accessor :objects
  
  def initialize(app=nil)
    super(app)
    @objects = {}
  end
  
  # GET /
  def index
    erb :index, :locals => {:objects => objects}
  end
  
  # GET /id
  def show(id)
    if object = objects[id]
      erb :show, :locals => {:id => id, :object => object}
    else
      erb :unknown, :locals => {:id => id}
    end
  end
  
  # POST /id
  def create(id)
    return raise("no id specified") if id.nil?
    
    if objects.has_key?(id)
      raise("already exists: #{id}")
    else
      objects[id] = Object.new
      redirect "/#{id}"
    end
  end
  
  # PUT /id
  # POST /id?_method=put
  def update(id)
    objects[id].call(request.env)
    redirect "/#{id}"
  end

  # DELETE /id
  # POST /id?_method=delete
  def destroy(id)
    objects.delete(id)
    redirect "/"
  end
end

App.run! :host => 'localhost', :port => 8080