Не удается преобразовать fixnum в строку во время рейка db: create

Только что создал новое приложение для блога с использованием rails 3.0

моя модель проста:

class Post < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :post
end

Я использовал команды: rails generate scaffold post title: string body: text etc.

для создания этих файлов.

Теперь я хотел сгенерировать базу данных с помощью:

rake db: create

Я получил ошибку:

rake aborted!
can't convert Fixnum into String

Есть идеи, в чем может быть проблема?

Я следую этот учебник: http://sixrevisions.com/web-development/how-to-create-a-blog-from-scratch-using-ruby-on-rails/

Вот след:

** Invoke db:create (first_time)
** Invoke db:load_config (first_time)
** Invoke rails_env (first_time)
** Execute rails_env
** Execute db:load_config
** Execute db:create
rake aborted!
can't convert Fixnum into String
/Library/Ruby/Gems/1.8/gems/mysql2-0.2.4/lib/mysql2/client.rb:36:in `connect'
/Library/Ruby/Gems/1.8/gems/mysql2-0.2.4/lib/mysql2/client.rb:36:in `initialize'
/Library/Ruby/Gems/1.8/gems/mysql2-0.2.4/lib/active_record/connection_adapters/mysql2_adapter.rb:14:in `new'
/Library/Ruby/Gems/1.8/gems/mysql2-0.2.4/lib/active_record/connection_adapters/mysql2_adapter.rb:14:in `mysql2_connection'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:230:in `send'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:230:in `new_connection'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:238:in `checkout_new_connection'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:194:in `checkout'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:190:in `loop'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:190:in `checkout'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:189:in `checkout'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:96:in `connection'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:318:in `retrieve_connection'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_specification.rb:97:in `retrieve_connection'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_specification.rb:89:in `connection'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/railties/databases.rake:68:in `create_database'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0/lib/active_record/railties/databases.rake:33
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `call'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:in `invoke_with_call_chain'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in `invoke'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:in `invoke_task'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/bin/rake:31
/usr/bin/rake:19:in `load'
/usr/bin/rake:19

database.yaml:

# MySQL.  Versions 4.1 and 5.0 are recommended.
#
# Install the MySQL driver:
#   gem install mysql2
#
# And be sure to use new-style password hashing:
#   http://dev.mysql.com/doc/refman/5.0/en/old-client.html
development:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: myblog_development
  pool: 5
  username: root
  password: 123
  socket: /tmp/mysql.sock

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: myblog_test
  pool: 5
  username: root
  password: 123
  socket: /tmp/mysql.sock

production:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: myblog_production
  pool: 5
  username: root
  password: 123
  socket: /tmp/mysql.sock

миграции:

class CreatePosts < ActiveRecord::Migration
  def self.up
    create_table :posts do |t|
      t.string :title
      t.text :body

      t.timestamps
    end
  end

  def self.down
    drop_table :posts
  end
end

следующая миграция:

class CreateComments < ActiveRecord::Migration
  def self.up
    create_table :comments do |t|
      t.string :name
      t.text :body
      t.references :post

      t.timestamps
    end
  end

  def self.down
    drop_table :comments
  end
end