I Need to Generate Uuid for My Rails Application. What Are the Options(Gems) I Have

I need to generate uuid for my rails application. What are the options(gems) I have?

There are plenty of options, I recommend not to add additional dependencies and use SecureRandom which is builtin:

SecureRandom.uuid #=> "1ca71cd6-08c4-4855-9381-2f41aeffe59c"

See other possible formats here.

Generating GUIDs in Ruby

As of Ruby 1.9, uuid generation is built-in. Use the SecureRandom.uuid function.

For example:

require 'securerandom'
SecureRandom.uuid # => "96b0a57c-d9ae-453f-b56f-3b154eb10cda"

Generating a short UUID string using uuidtools In Rails

You don't need uuidtools for this. You can use Secure Random for this.

[1] pry(main)> require "securerandom"
=> true
[2] pry(main)> SecureRandom.hex(20)
=> "82db4d707c4c5db3ebfc349da09c991b7ca0faa1"
[3] pry(main)> SecureRandom.base64(20)
=> "CECjUqNvPBaq0o4OuPy8RvsEoCY="

Passing 4 and 5 to hex will generate 8 and 10 character hex strings respectively.

[5] pry(main)> SecureRandom.hex(4)
=> "a937ec91"
[6] pry(main)> SecureRandom.hex(5)
=> "98605bb20a"

Ruby UUID and uniqueness, for an ID

No way. UUID is considered unique because it is very long and it is practically impossible to generate same UUIDs. If you trim it to 6 chars then you drammatically increase possiblility of duplicate. You have to use either incrementing id or full UUID.

Only deterministic generation (id(x + 1) = id(x) + 1) can guarantee uniqueness. UUID doesn't guarantee it and 6 chars guarantee it even less.

Other option is to create ID generation service, it will have single method getNewId and will keep knowledge that will be enought to provide unique ids. (Simplest case - counter)

Ruby on Rails 4.2 with Globalize gem for UUID table

I was not able to use the hardcoded solution provided by Thomas Engelbrecht because not all my models use uuid.

Since the model is delegated we can check it's primary key type by adding a method :

def primary_key_type
    column_type(model.primary_key).to_sym
end

And i'm using Rails 4.2 so I can use the references type option ( source )

module Globalize
  module ActiveRecord
    module Migration
      class Migrator
        def primary_key_type
          column_type(model.primary_key).to_sym
        end

        def create_translation_table
          connection.create_table(translations_table_name, id: primary_key_type) do |t|
            t.references table_name.sub(/^#{table_name_prefix}/, '').singularize, null: false, type: primary_key_type
            t.string :locale, null: false
            t.timestamps null: false
          end
        end
      end
    end
  end
end

There must be a cleaner way, but I lack the experience to create a pull request.

UUIDs in Rails3

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

Generate valid, deterministic UUIDs for tests

UUIDs use two digits to denote their format: (actually just some of the digit's bits)

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
              ^    ^
        version    variant

The following pattern denotes version 4 (M=4), variant 1 (N=8) which simply means "random bytes":

xxxxxxxx-xxxx-4xxx-8xxx-xxxxxxxxxxxx

You could use it as a template to generate fake (but valid) UUIDs based on a sequence number: (as suggested in the comments)

def fake_uuid(n)
  '00000000-0000-4000-8000-%012x' % n
end

fake_uuid(1) #=> "00000000-0000-4000-8000-000000000001"
fake_uuid(2) #=> "00000000-0000-4000-8000-000000000002"
fake_uuid(3) #=> "00000000-0000-4000-8000-000000000003"

Having it somewhat readable is a big pro ...

There are plenty of unused fields / digits to add more data:

def fake_uuid(klass, n)
  k = { Company => 1, Employee => 2 }.fetch(klass, 0)

  '%08x-0000-4000-8000-%012x' % [k, n]
end

fake_uuid(Company, 1)   #=> "00000001-0000-4000-8000-000000000001"
fake_uuid(Company, 2)   #=> "00000001-0000-4000-8000-000000000002"

fake_uuid(Employee, 1)  #=> "00000002-0000-4000-8000-000000000001"
fake_uuid(Employee, 2)  #=> "00000002-0000-4000-8000-000000000002"

#                            ^^^^^^^^                ^^^^^^^^^^^^
#                              class                   sequence

RoR roles management - rolify gem - use with resources of both UUID and Integer IDs

Well, you should just add a migrations to the database tables that you want to use UUID on. rails g migration add_uuid_to_sometablename , and should be sufficient.

And if you need to index that particular column, you can say like

add_index(:yourtablename, :uuid, unique: true)

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