# lib/extensions/statuses.rb
class ActiveRecord::Base
  def self.has_statuses(*status_names)
    validates :status,
      :presence => true,
      :inclusion => { :in => status_names }
      
    # Status Finders
    status_names.each do |status_name|
      scope "all_#{status_name}", where(:status => status_name)
    end

    # Status Accessors
    status_names.each do |status_name|
      define_method "#{status_name}?" do
        status == status_name
      end
    end
  end
end

class Purchase < ActiveRecord::Base
  has_statuses %w(in_progress submitted approved partially_shipped fully_shipped)

  scope :all_not_shipped, where(status: ["partially_shipped", "fully_shipped"])

  def not_shipped?
    !(partially_shipped? or fully_shipped?)
  end
end

def change
  add_column :purchases, :status, :string, default: ""
end