Refactor1.rb

class Article < ActiveRecord::Base

  def self.states(*states)
    states.each do |state|
      define_method "#{state}?" do
        self.state == state
      end
      
      define_singleton_method "all_#{state}" do
        where("state = ?", state)
      end
    end
  end

  states :draft, :published, :spam

end

Refactor2.rb

module Statable
  def states(*states)
    states.each do |state|
      define_method "#{state}?" do
        self.state == state
      end
      
      define_singleton_method "all_#{state}" do
        where("state = ?", state)
      end
    end
  end
end

class Article < ActiveRecord::Base
  extend Statable

  states :draft, :published, :spam
end