How to add memcached gem(Dalli) to Heroku with Sinatra

gistfile1.rb

# Herodu Dev Center Doc:
# http://devcenter.heroku.com/articles/memcache
# Dalli gem heroku url:
# https://github.com/mperham/dalli

#######################
# Local Setup memcached
#######################

sudo port install memcached

# run the memcached daemon:
memcached -vv

#######################
#Using Memcache with Sinatra
#######################

# add gem to .gems (or Gemfile)
dalli

# install the gem
sudo gem install dalli

# require it first
require "dalli"

# add cache setting to yourapp.rb
# eg.cache for 10 min here. deault options is never expire
cache = Dalli::Client.new(nil, {:expires_in => 60*10})
set :cache, cache

# how to use
settings.cache.set('color', 'blue')
settings.cache.get('color')  # => 'blue'

#######################
# Deploy to Heroku
#######################

heroku addons:add memcache