How I set up my Rails 3 User model to have a pretty URL/ID "slug" without adding a slug field to the database

routes.rb

resources :users
#plus any applicable authentication routing code, e.g., devise_for :users

user.rb

class User < ActiveRecord::Base

  def slug
    "#{id}-#{name}".parameterize
  end

  def to_param
    slug
  end

  def self.find_by_slug(*args)
    record = find(*args)
    if record and record.respond_to? :slug
      return nil unless record.slug == args.first
    end
    record
  end

  def self.find_by_slug!(*args)
    find_by_slug(*args) or raise ActiveRecord::RecordNotFound
  end
  
  def firstname
    self.name.match(/^([\w]+)/i )[1].titlecase # a handy bonus class method if you're storing the User's full name in a single field and want to grab just their first name.  For example, call in the view via @user.firstname
  end

end

User_slugs_without_database.rb

#This is how I set up my Rails 3 User model to have a pretty URL/ID "slug" without adding a slug field to the database

users_controller.rb

class UsersController < ApplicationController

  def show #example action
    @user = User.find_by_slug(params[:id])
  end

end