Sluggable rails concern: use slugs instead of ids in the url!

sluggable.rb

module Sluggable
  extend ActiveSupport::Concern
  cattr_reader :slugging
  
  included do
    before_save :generate_slug
    
    def self.sluggable
      all.extending(Sluggable::Finder)
    end

    def self.slugging attribute
      @@slugging = attribute.to_sym
    end
  end

  def to_param?
    return nil unless persisted?
    slug
  end

  module Finder
    def find(*args)
      id = args.first
      return super if args.count != 1
      resource = resource_by_slug(id)
      resource ||= super
      raise ActiveRecord::RecordNotFound unless resource
      resource
    end

  private
    def resource_by_slug(id)
      find_by(slug: id)
    end
  end

private
  def generate_slug
    return unless send("#{slugging}_changed?".to_sym)
    self.slug = send(slugging).parameterize
  end
end

I ran into some issues implementing this. The @@slugging is a class variable shared throughout the classes that includes the Slug concern. This becomes an issue if I want to use the concern on more than one class, for example:

class Person < ApplicationRecord
  include Sluggable
  slugging :name
  
  ...
end

class Company < ApplicationRecord
  include Sluggable
  slugging :alias
end

When rails loads my classes, the slugging method sets the @@slugging == :name at first and then sets @@slugging == :alias, making it only work when I am dealing with Company objects. If I want to update the slug of a Person, I get a undefined method 'alias_changed?' error for a Person.

I think that the best approach would be defining the class variable for each class using the concern with an cattr_accessor.

Hey! yes, you are right, I came across the same problem long time ago and always forgot to fix it in this gist. Did it now! Thanks for the heads up!