gistfile1.rb

require 'dm-core'
require 'dm-validations'
require 'dm-timestamps'

DataMapper.setup(:default, "sqlite3://#{Dir.pwd}/mydb.sqlite3")

class Post
  include DataMapper::Resource

  has n, :comments

  # The Serial type provides auto-incrementing primary keys
  property :id,         Serial
  # ...or pass a :key option for a user-set key like the name of a user:
  property :name,       String, :key => true
end

class Comment
  include DataMapper::Resource

  belongs_to :post

  property :id,         Serial
  property :email,      String
end

DataMapper.auto_upgrade!

def create_post(rname)
  p = Post.new({:name => rname})
  p.save
end

def add_comment(p_id, pair_data)
  #p = Post.first({:id =>1})
  p = Post.get(1)
  c = p.comments.build(pair_data)
  c.save
end