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What is noid-rails?

This gem mints identifiers for models in your Rails-based application with opaque Noid-based identifiers.

This gem depends only upon Rails, not on ActiveFedora

Product Owner & Maintenance

noid-rails is a Core Component of the Samvera community. The documentation for what this means can be found here. ### Product Owner Justin Coyne

Table of Contents


Add this line to your application's Gemfile:

gem 'noid-rails'

And then execute:

$ bundle install

Or install it yourself via:

$ gem install noid-rails


Minting and validating identifiers

Mint a new Noid:

noid_service =
noid =

This creates a Noid with the default identifier template, which you can override (see below). Now that you have a service object with a template, you can also use it to validate identifiers to see if they conform to the template:

noid_service.valid? 'xyz123foobar'
> false

ActiveFedora integration

To get ActiveFedora to automatically call your Noid service whenever a new ActiveFedora object is saved, include the Noid::Rails::Model, e.g.:

# app/models/my_object.rb
require 'noid-rails'

class MyObject < ActiveFedora::Base  ## This overrides the default behavior, which is to ask Fedora for an id
  # @see ActiveFedora::Persistence.assign_id

  def assign_id


  def service
    @service ||=

Identifier/URI translation

As Noid::Rails overrides the default identifier minting strategy in ActiveFedora, you will need to let ActiveFedora know how to translate identifiers into URIs and vice versa so that identifiers are laid out in a sustainable way in Fedora. Add the following to e.g. config/initializers/active_fedora.rb:

baseparts = 2 + [(Noid::Rails::Config.template.gsub(/\.[rsz]/, '').length.to_f / 2).ceil, 4].min
ActiveFedora::Base.translate_uri_to_id = lambda do |uri|
                                           uri.to_s.sub(baseurl, '').split('/', baseparts).last
ActiveFedora::Base.translate_id_to_uri = lambda do |id|

This will make sure your objects have Noid-like identifiers (e.g. bb22bb22b) that map to URIs in Fedora (e.g. bb/22/bb/22/bb22bb22b).

Overriding default behavior

The default minter in Noid::Rails is the file-backed minter to preserve default behavior.

To better support multi-host production installations that expect a shared database but not necessarily a shared filesystem (e.g., between load-balanced Rails applications), we highly recommend swapping in the database-backed minter.

Use database-based minter state

The database-based minter stores minter state information in your application's relational database. To use it, you'll first need to run the install generator:

$ rails generate active_fedora:noid:install

This will create the necessary database migrations.

Then run rake db:migrate

To start minting identifiers with the new minter, override the AF::Noid configuration in e.g. config/initializers/noid-rails.rb:

require 'active_fedora/noid'

Noid::Rails.configure do |config|
  config.minter_class = Noid::Rails::Minter::Db

Using the database-backed minter can cause problems with your test suite, where it is often sensible to wipe out database rows between tests (which destroys the database-backed minter's state, which renders it unusable). To deal with this and still get the benefits of using the database-backed minter in development and production environments, you'll also want to add the following helper to your spec/spec_helper.rb:

require 'active_fedora/noid/rspec'

RSpec.configure do |config|
  include Noid::Rails::RSpec

  config.before(:suite) { disable_production_minter! }
  config.after(:suite)  { enable_production_minter! }

If you switch to the new database-backed minter and want to include in that minter the state of your current file-backed minter, Noid::Rails 2.x provides a new rake task that will copy your minter's state from the filesystem to the database:

# For migrating minter state from a file to a database
$ rake noid:rails:migrate:file_to_database
# For migrating minter state from a database to a file
$ rake noid:rails:migrate:database_to_file

Identifier template

To override the default identifier pattern -- a nine-character string consisting of two alphanumeric digits, two numeric digits, two alphanumeric digits, two numeric digits, and a check digit -- put the following code in e.g. config/initializers/noid-rails.rb:

require 'noid-rails'

Noid::Rails.configure do |config|
  config.template = '.ddddd'

For more information about the format of Noid patterns, see pages 8-10 of the Noid documentation.

Custom minters

If you don't want your minter's state to be persisted, you may also write and configure your own minter. First write up a minter class that looks like the following:

class MyMinter < Noid::Rails::Minter::Base
  def valid?(identifier)
    # return true/false if you care about ids conforming to templates

  def read    # return current minter state


  def write!(state)
    # write a passed-in minter state


  def next_id    # return the next identifier from the minter


Then add your new minter class to the Noid::Rails configuration (config/initializers/noid-rails.rb):

require 'noid-rails'

Noid::Rails.configure do |config|
  config.minter_class = MyMinter

And the service will delegate minting and validating to an instance of your customized minter class.


The Samvera community is here to help. Please see our support guide.


This software has been developed by and is brought to you by the Samvera community. Learn more at the Samvera website.

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