save user and associated referrals in one command

gistfile1.txt

peterv@ASUS:~/b/rails-apps/apps/temp/base_app$ rails g model User
      invoke  active_record
      create    db/migrate/20111011103622_create_users.rb
      create    app/models/user.rb
      invoke    rspec
      create      spec/models/user_spec.rb
      invoke      factory_girl
      create        spec/factories/users.rb

peterv@ASUS:~/b/rails-apps/apps/temp/base_app$ rails g model Referral
      invoke  active_record
      create    db/migrate/20111011103641_create_referrals.rb
      create    app/models/referral.rb
      invoke    rspec
      create      spec/models/referral_spec.rb
      invoke      factory_girl
      create        spec/factories/referrals.rb

peterv@ASUS:~/b/rails-apps/apps/temp/base_app$ vim db/migrate//20111011103622_create_users.rb 
peterv@ASUS:~/b/rails-apps/apps/temp/base_app$ cat db/migrate//20111011103622_create_users.rb 
class CreateUsers < ActiveRecord::Migration
  def change
    create_table :users do |t|
      t.string :name
      t.timestamps
    end
  end
end

peterv@ASUS:~/b/rails-apps/apps/temp/base_app$ vim db/migrate/20111011103641_create_referrals.rb 
peterv@ASUS:~/b/rails-apps/apps/temp/base_app$ cat db/migrate/20111011103641_create_referrals.rb 
class CreateReferrals < ActiveRecord::Migration
  def change
    create_table :referrals do |t|
      t.references :user
      t.string :comment
      t.timestamps
    end
  end
end

peterv@ASUS:~/b/rails-apps/apps/temp/base_app$ rake db:migrate
==  CreateUsers: migrating ====================================================
-- create_table(:users)
NOTICE:  CREATE TABLE will create implicit sequence "users_id_seq" for serial column "users.id"
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "users_pkey" for table "users"
   -> 0.0304s
==  CreateUsers: migrated (0.0305s) ===========================================

==  CreateReferrals: migrating ================================================
-- create_table(:referrals)
NOTICE:  CREATE TABLE will create implicit sequence "referrals_id_seq" for serial column "referrals.id"
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "referrals_pkey" for table "referrals"
   -> 0.0165s
==  CreateReferrals: migrated (0.0166s) =======================================

peterv@ASUS:~/b/rails-apps/apps/temp/base_app$ rails c
Loading development environment (Rails 3.1.1.rc1)
001:0> u = User.new(:name => "Peter")
=> #<User id: nil, name: "Peter", created_at: nil, updated_at: nil>
002:0> r1 = u.referrals.build(:comment => "sailor")
=> #<Referral id: nil, user_id: nil, comment: "sailor", created_at: nil, updated_at: nil>
003:0> r2 = u.referrals.build(:comment => "developer")
=> #<Referral id: nil, user_id: nil, comment: "developer", created_at: nil, updated_at: nil>
004:0> u.save
   (0.4ms)  BEGIN
  SQL (77.3ms)  INSERT INTO "users" ("created_at", "name", "updated_at") VALUES ($1, $2, $3) RETURNING "id"  [["created_at", Tue, 11 Oct 2011 10:56:14 UTC +00:00], ["name", "Peter"], ["updated_at", Tue, 11 Oct 2011 10:56:14 UTC +00:00]]
  SQL (1.0ms)  INSERT INTO "referrals" ("comment", "created_at", "updated_at", "user_id") VALUES ($1, $2, $3, $4) RETURNING "id"  [["comment", "sailor"], ["created_at", Tue, 11 Oct 2011 10:56:14 UTC +00:00], ["updated_at", Tue, 11 Oct 2011 10:56:14 UTC +00:00], ["user_id", 2]]
  SQL (0.4ms)  INSERT INTO "referrals" ("comment", "created_at", "updated_at", "user_id") VALUES ($1, $2, $3, $4) RETURNING "id"  [["comment", "developer"], ["created_at", Tue, 11 Oct 2011 10:56:14 UTC +00:00], ["updated_at", Tue, 11 Oct 2011 10:56:14 UTC +00:00], ["user_id", 2]]
   (0.9ms)  COMMIT
=> true
005:0> u
=> #<User id: 2, name: "Peter", created_at: "2011-10-11 10:56:14", updated_at: "2011-10-11 10:56:14">
006:0> r1
=> #<Referral id: 2, user_id: 2, comment: "sailor", created_at: "2011-10-11 10:56:14", updated_at: "2011-10-11 10:56:14">
007:0> r2
=> #<Referral id: 3, user_id: 2, comment: "developer", created_at: "2011-10-11 10:56:14", updated_at: "2011-10-11 10:56:14">

peterv@ASUS:~/b/rails-apps/apps/temp/base_app$ vim app/models/referral.rb # adding a validation that will fail on child
peterv@ASUS:~/b/rails-apps/apps/temp/base_app$ cat app/models/referral.rb 
class Referral < ActiveRecord::Base
  belongs_to :user
  validates :comment, :presence => true
end

peterv@ASUS:~/b/rails-apps/apps/temp/base_app$ rails c
Loading development environment (Rails 3.1.1.rc1)
001:0> u2 = User.new(:name => "Jan")
=> #<User id: nil, name: "Jan", created_at: nil, updated_at: nil>
002:0> r1 = u2.referrals.build(:comment => "wanderer")
=> #<Referral id: nil, user_id: nil, comment: "wanderer", created_at: nil, updated_at: nil>
003:0> r2 = u2.referrals.build
=> #<Referral id: nil, user_id: nil, comment: nil, created_at: nil, updated_at: nil>
004:0> u2.save
   (0.4ms)  BEGIN
   (0.4ms)  ROLLBACK
=> false
005:0> User.find_by_name("Jan")
  User Load (1.9ms)  SELECT "users".* FROM "users" WHERE "users"."name" = 'Jan' LIMIT 1
=> nil
006:0> User.find_by_name("Peter")
  User Load (0.9ms)  SELECT "users".* FROM "users" WHERE "users"."name" = 'Peter' LIMIT 1
=> #<User id: 2, name: "Peter", created_at: "2011-10-11 10:56:14", updated_at: "2011-10-11 10:56:14">