From: Brian Candler <b.candler@...>
Date: 2009-01-20T19:17:28+09:00
Subject: Re: Desktop <-> Web

Thomas Sawyer wrote:
> ultimately I want to
> use Rack instead. An example of a simple Rack-based JSON servlet would
> be awesome. Anyone have one?

How about this with Sinatra, which sits on top of Rack:

--- myapp.rb ---
require 'rubygems'
require 'sinatra'
require 'json'
require 'widget'

get '/widgets.json' do
  Widget.all.to_json
end

get '/widgets/:id.json' do
  Widget.find(Integer(params[:id])).to_json
end

post '/widgets.json' do
  item = JSON.parse(request.body.read)
  raise "Bad object" unless item.is_a? Widget
  Widget.add(item).to_s
end

--- widget.rb ---
# Rubbish model, not thread-safe!
class Widget
  attr_accessor :id, :name, :price
  def initialize(id, name, price)
    @id, @name, @price = id, name, price
  end
  def to_json(*a)
    {
      'json_class' => self.class.name,
      'data' => [ @id, @name, @price ],
    }.to_json(*a)
  end
  def self.json_create(o)
    new *o['data']
  end
  def self.all
    @all ||= []
  end
  def self.add(item)
    @seq ||= 0
    @seq += 1
    item.id = @seq
    all << item
    return @seq
  end
  def self.create(*args)
    add(new(*args))
  end
  def self.find(id)
    all.find { |item| item.id == id }
  end
end
Widget.create(nil, "flurble", 12.3)
Widget.create(nil, "boing", 4.56)
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