懒惰注册sinatra和datamapper

class User
  include DataMapper::Resource

  property :id,                 Serial
  property :email,              String, :required => true, :unique => true, :format  => :email_address,
  property :name,               String
  property :hashed_password,    String
  property :salt,               String  
  property :created_at,         DateTime

  attr_accessor :password, :password_confirmation

  validates_presence_of     :password_confirmation
  validates_presence_of     :password
  validates_length_of       :password, :min => 6
  validates_confirmation_of :password
end