extending_active_record.rb

# config/initializers/extensions.rb

ActiveRecord::Base.send(:include, StatusField)
ActiveRecord::Base.send(:include, SlugUrl)

# lib/status_field.rb

module StatusField
  def self.included(base)
    base.extend ClassMethods
  end

  module ClassMethods
    def status_field(*args)
      args.each do |arg|
        define_method("status_#{arg}?") { status == arg.to_s }
        define_method("status_#{arg}")  { self.status = arg.to_s }
      end
    end
  end
end

# lib/slug_url.rb

module SlugUrl
  def self.included(base)
    base.extend ClassMethods
  end

  module ClassMethods
    def slug_url(attr)
      define_method("to_param") { send(attr) }
      instance_eval %{
        def find(*args, &block)
          if block_given? || args.length != 1
            super
          else
            find_by_#{attr}!(args[0])
          end
        end
      }
    end
  end
end