gistfile1.rb

require 'rubygems'
require 'sinatra'
require 'json'

class Person

  attr_accessor :first, :last

  def initialize(first, last)
    @first = first
    @last = last
  end 

  def to_json
    ["first" => @first, "last" => @last].to_json
  end 

end

people = [ 
  Person.new('Alan', 'Dipert'),
  Person.new('Micha', 'Niskin'),
  Person.new('Oren', 'Niskin'),
  Person.new('Albert', 'Einstein')
]

before do
  content_type 'text/json'
end

put '/person/:id/' do
  id = params[:id].to_i
  people[id].first = params[:first]
  people[id].last = params[:last]
  people[id].to_json
end

get '/person/:id/' do
  people[params[:id].to_i].to_json
end

get '/person/' do
  people.to_json
end