heroku_db_sample.rb

app.rb

require 'bundler'
Bundler.setup

require 'sinatra'
require 'dm-core'
require 'dm-migrations'

get '/' do
  Person.first.name
end

class Person
  include DataMapper::Resource

  property :id,   Serial
  property :name, String
end

DataMapper.setup(:default, ENV['DATABASE_URL'])
DataMapper.finalize
DataMapper.auto_migrate!

Person.create(:name => 'HOGE')

config.ru

require './app'
run Sinatra::Application

Gemfile

source 'http://rubygems.org'

gem 'sinatra'
gem 'dm-core'
gem 'dm-postgres-adapter'