Rails3中的UUID

Question

I'm trying to setup my first Rails3 project and, early on, I'm running into problems with either uuidtools , my UUIDHelper or perhaps callbacks. I'm obviously trying to use UUIDs and (I think) I've set things up as described in Ariejan de Vroom's article . I've tried using the UUID as a primary key and also as simply a supplemental field, but it seems like the UUIDHelper is never being called.

I've read many mentions of callbacks and/or helpers changing in Rails3, but I can't find any specifics that would tell me how to adjust. Here's my setup as it stands at this moment (there have been a few iterations):

# migration
class CreateImages < ActiveRecord::Migration
  def self.up
    create_table :images do |t|
      t.string :uuid, :limit  => 36
      t.string :title
      t.text :description

      t.timestamps
    end
  end
  ...
end

# lib/uuid_helper.rb
require 'rubygems'
require 'uuidtools'

module UUIDHelper
  def before_create()
    self.uuid = UUID.timestamp_create.to_s
  end
end

# models/image.rb
class Image < ActiveRecord::Base
  include UUIDHelper

  ...
end

Any insight would be much appreciated.

Thanks.

Answer 1

If you get an error "NoMethodError (undefined method `timestamp_create' for UUID:Class)", then change the contents of the set_uuid method to:

self.uuid = UUIDTools::UUID.timestamp_create().to_s

I believe this is necessary for more recent versions of the uuidtools gem.

Answer 2

Are you declaring another before_create method in your Image model? If so, you'll be overriding the one in the UUIDHelper module. You'll want to either declare the callback a different manner, or call super in the callback in your image model.

Edit: Maybe change the helper to look something like this:

module UUIDHelper
  def self.included(base)
    base.class_eval do
      before_create :set_uuid

      def set_uuid
        self.uuid = UUID.timestamp_create.to_s
      end
    end
  end
end

Answer 3

I outline a working UUID example in this question:

Is COMB GUID a good idea with Rails 3.1 if I use GUIDs for primary keys?

Obviously you can rewrite set_uuid any way you want--you don't have to use COMB GUIDs.

Credits: adapted from https://github.com/boriscy/uuidrails3/blob/master/lib/uuid_helper.rb referenced in using UUID as primary key in rails and polymorph relationships . Also found an example at https://github.com/belucid/Recent-Updates/blob/884624e433cdffd63abd24b3bdb516a5d1596173/lib/uuid_helper.rb .

Answer 4

I also noticed you're missing the :id => false in your create_table . Check out the example from Ariejan's article a little more closely:

create_table :posts, :id => false do |t|
  t.string :uuid, :limit => 36, :primary => true
end

Additionally, I prefer the UUIDTools::UUID.random_create.to_s to the timestamp version. YMMV.

Answer 5

I had to specify the primary key in my model to make it work at the controller level.

class Image < ActiveRecord::Base
  include UUIDHelper
  set_primary_key :uuid

  ...

end

Answer 6

You might consider avoiding the use of string types to store your UUID, as it will make lookups super-slow. There is an 'activeuuid' gem that looks promising (uses binary storage).