##Migration - 008_create_actors.rb
class CreateActors < ActiveRecord::Migration

  def self.up
    create_table :actors do |table|
      table.column :name,               :string,  :null => false, :limit => 255
      table.column :actor_type_id,      :integer, :null => false
      table.column :project_version_id, :integer, :null => false
      table.column :position,           :integer, :null => false

      table.column :created_at, :datetime
      table.column :updated_at, :datetime
      table.column :lock_version, :integer, :null => false, :default => 0
    end

    add_index :actors, :project_version_id
    add_index :actors, :lock_version
    add_index :actors, [:name, :project_version_id], :unique => true, :name => 'actors_nameproject_version_id_index'
  end

  def self.down
    drop_table :actors
  end
end

##Model - actor.rb
class Actor < ActiveRecord::Base
  validates_presence_of :name, :project_version_id, :position
  validates_length_of :name, :in => 1..255
  validates_uniqueness_of :name, :scope => :project_version_id
  validates_numericality_of :actor_type_id, :project_version_id, :position, :only_integer => true

  belongs_to :project_version
  belongs_to :actor_type
  acts_as_list :scope => :project_version
end

##MySQL info
mysql> describe actors;
+--------------------+--------------+------+-----+---------+----------------+
| Field              | Type         | Null | Key | Default | Extra          |
+--------------------+--------------+------+-----+---------+----------------+
| id                 | int(11)      | NO   | PRI | NULL    | auto_increment |
| name               | varchar(255) | NO   | MUL | NULL    |                |
| actor_type_id      | int(11)      | NO   |     | NULL    |                |
| project_version_id | int(11)      | NO   | MUL | NULL    |                |
| position           | int(11)      | NO   |     | NULL    |                |
| created_at         | datetime     | YES  |     | NULL    |                |
| updated_at         | datetime     | YES  |     | NULL    |                |
| lock_version       | int(11)      | NO   | MUL | 0       |                |
+--------------------+--------------+------+-----+---------+----------------+
8 rows in set (0.01 sec)

##Test - actor_test.rb
def test_creation
  actor = Actor.new()
  assert !actor.valid?                                #passes
  assert actor.errors.invalid?(:name)                 #passes
  assert actor.errors.invalid?(:position)             #fails
  assert actor.errors.invalid?(:project_version_id)   #fails
  assert actor.errors.invalid?(:actor_type_id)        #fails
end