datamapper: simple associations

app.rb

require 'data_mapper'

DataMapper::Logger.new($stdout, :debug)
DataMapper.setup(:default, "sqlite3://#{Dir.pwd}/example.db")

class Post
  include DataMapper::Resource

  property :id, Serial
  property :text, Text

  has n, :comments
end

class Comment
  include DataMapper::Resource

  property :id,     Serial
  property :text, Text

  belongs_to :post  # defaults to :required => true

end

DataMapper.finalize

require  'dm-migrations'

#DataMapper.auto_migrate!
DataMapper.auto_upgrade!