application.rb

class Application < Sinatra::Base
  register SinatraMore::MarkupPlugin
  register SinatraMore::RenderPlugin
  
  configure :development do
    DataMapper::setup(:default, "sqlite3://#{Dir.pwd}/db/app.db")
  end
  
  class User
    include DataMapper::Resource

    property :id,         Serial
    property :username,   String, :nullable => false
    property :email,      String, :nullable => false
    property :created_at, DateTime
  end
  
  configure :development do
    DataMapper.auto_upgrade!
  end
  
  before do
    headers "Content-Type" => "text/html; charset=utf-8"
  end
  
  get '/' do
    @user = User.new
    haml :index
  end
end

config.ru

require 'rubygems'
require 'sinatra/base'
require 'sinatra_more'
require 'dm-core'
require 'dm-validations'
require 'dm-timestamps'
require 'haml'

require 'application'

map '/' do
    run Application
end

index.haml

#index
  - form_for @user, '/register' do |f|
    = f.error_messages
    = f.text_field_block :name
    = f.text_field_block :email
    = f.submit_block "Create"