simply_stated

  ActiveRecord::Schema.define :version => 0 do
    create_table :users, :force => true do |t|
      t.column :name, :string
      t.column :state, :string, :default => "new"
    end
  end

class User
  include SimplyStated
  
  state :new do
    transitions { self.state = :has_name if name.present? }
  end
  
  state :has_name do
    transitions { self.state = :had_name if name.blank? }
  end
  
  state :had_name
end

user = User.create
user.state #=> :new

user.update_attributes! :name => "Lombardo"
user.state #=> :has_name

user.update_attributes! :name => ""
user.state #=> :had_name

user.state = :explosion #=> raises "invalid state explosion"