Very basic rack application showing how to use a router based on the uri and how to process requests based on the HTTP method used.

rack_example.ru

#########################################
# Very basic rack application showing how to use a router based on the uri
# and how to process requests based on the HTTP method used.
#
# Usage:
# $ rackup rack_example.ru
#
# $ curl -X POST -d 'title=retire&body=I should retire in a nice island' localhost:9292/ideas
# $ curl -X POST -d 'title=ask Satish for a gift&body=Find a way to get Satish to send me a gift' localhost:9292/ideas
# $ curl localhost:9292/ideas
#
#########################################

class Idea
  attr_accessor :title, :body, :created_at

  # Memory store, gets cleared as the process is restarted
  def self.store
    @ideas ||= []
  end

  class InvalidParams < StandardError; end
  
  # create an instance based on some passed params
  def initialize(params)
    raise InvalidParams, "You need to provide at least a title" unless params['title']
    self.title = params['title']
    self.body = params['body']
    self.created_at = Time.now
  end

  # Converts an instance into a string
  def to_s
    "#{title} at #{created_at.to_s}\n#{body}"
  end
end

class IdeaAPI
  def call(env)
    case env['REQUEST_METHOD']
    when 'POST'
      Idea.store << Idea.new(request.params)
      return [200, {"Content-Type" => "text/plain"}, ["Idea added, currently #{Idea.store.size} ideas are in memory!"]]
    when 'GET'
      return [200, {"Content-Type" => "text/plain"}, [Idea.store.map{|idea, idx| idea.to_s }.join("\n\n") + "\n"]]
    end if env['PATH_INFO'] == '/ideas'
    [404, {}, ["Did you get lost?"]]
  rescue Idea::InvalidParams => error
    [400, {"Content-Type" => "text/plain"}, [error.message]]
  end
end

run IdeaAPI.new

request would be undefined in this line: Idea.store << Idea.new(request.params)