Creates :slug from given :title if no :slug given

sluggable_model.rb

# app/models/concerns/sluggable_model.rb
#
# https://gist.github.com/firedev/9701874
#
# Usage:
#
# rails g migration addSlugToModel slug:string:uniq
#
# include SluggableModel
# attr_slug :title [, :slug] [, &block]
#
# Creates :slug from given :title when saving models if no :slug given
# Uses parameterize by default or can run :title through a &block:
#
# include SluggableModel
# attr_slug :title # default handler is .parameterize
#
# or you can pass a block with your own handler:
# attr_slug(:title [, :slug]) { |title| title.transliterate.parameterize }
#

module SluggableModel
  extend ActiveSupport::Concern

  module ClassMethods
    def attr_slug(title_attr, slug_attr = :slug, &block)
      before_validation { create_slug(title_attr, slug_attr, &block) }
      validates slug_attr, presence: true, uniqueness: true if respond_to? slug_attr
    end
  end

  def to_param
    "#{id}-#{slug}"
  end

  def create_slug(title_attr, slug_attr, &block)
    return if send(title_attr).blank?
    send "#{slug_attr}=", create_slug_string(title_attr, &block)
  end

  def create_slug_string(title_attr, &_block)
    if block_given?
      yield send(title_attr).to_s
    else
      send(title_attr).to_s.parameterize
    end
  end
end