module Slugification
  extend ActiveSupport::Concern

  module ClassMethods
    def slugify(name, opts={})
      _opts = opts.reverse_merge(:if => lambda{ |obj| obj.send("#{name}_changed?".to_sym) })
      before_validation -> { self.slug = slugify(self.send(name.to_sym)) }, _opts
    end
  end

  private

  def slugify(str)
    str.gsub(/\s/,'_').dasherize.downcase
  end
end