# Problems using UUID (universally unique identifier)

**URL:** <https://www.ruby-forum.com/t/problems-using-uuid-universally-unique-identifier/140301>\
**Category:** Ruby\
**Created:** [June 12, 2008, 7:20pm UTC](https://www.ruby-forum.com/t/problems-using-uuid-universally-unique-identifier/140301 "2008-06-12T19:20:18Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![pabloq](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/ec9cab/32.png) [@pabloq](https://www.ruby-forum.com/u/pabloq)\
**Post date:** [June 12, 2008, 7:20pm UTC](https://www.ruby-forum.com/t/problems-using-uuid-universally-unique-identifier/140301/1 "2008-06-12T19:20:18Z")

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Hi all,

I need to generate uuid numbers. I try to run this:

require\_gem ‘uuid’

10.times do  
p UUID.new  
end

But I’m receiving this:

183260c1-1ad1-012b-bfbf-001c23187f94  
uuid.rb:1:Warning: require\_gem is obsolete. Use gem instead.  
UUID: Initialized UUID generator with sequence number 0xbfbf and MAC  
address  
00-1C-23-18-7F-94

So I change require\_gem with gem. Now I’m receiving this:

uuid.rb:3: uninitialized constant UUID (NameError)

Tool completed with exit code 1

What am I doing wrong?

---

<div class="post-metadata">

**Author:** ![pabloq](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/ec9cab/32.png) [@pabloq](https://www.ruby-forum.com/u/pabloq)\
**Post date:** [June 12, 2008, 7:29pm UTC](https://www.ruby-forum.com/t/problems-using-uuid-universally-unique-identifier/140301/2 "2008-06-12T19:29:06Z")

</div>

On Thu, Jun 12, 2008 at 1:19 PM, Pablo Q. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> What am I doing wrong?

Just use require:

require ‘uuid’

–  
Avdi

Home: [http://avdi.org](http://avdi.org)  
Developer Blog: [Avdi Grimm, Code Cleric](http://avdi.org/devblog/)  
Twitter: [http://twitter.com/avdi](http://twitter.com/avdi)  
Journal: [http://avdi.livejournal.com](http://avdi.livejournal.com)

---

<div class="post-metadata">

**Author:** ![pabloq](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/ec9cab/32.png) [@pabloq](https://www.ruby-forum.com/u/pabloq)\
**Post date:** [June 12, 2008, 8:11pm UTC](https://www.ruby-forum.com/t/problems-using-uuid-universally-unique-identifier/140301/3 "2008-06-12T20:11:32Z")

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On Jun 12, 2008, at 1:27 PM, Avdi G. wrote:

> Home: [http://avdi.org](http://avdi.org)  
> Developer Blog: [Avdi Grimm, Code Cleric](http://avdi.org/devblog/)  
> Twitter: [http://twitter.com/avdi](http://twitter.com/avdi)  
> Journal: [http://avdi.livejournal.com](http://avdi.livejournal.com)

Or perhaps:

require ‘rubygems’  
require ‘uuid’

If you ever needed a specific version of UUID, you could add a gem  
statement:

require ‘rubygems’  
gem ‘uuid’, '~\> 1.0.4"  
require ‘uuid’

The example ‘~\> 1.0.4’ will be true for all 1.0.x versions where x \>=  
4, but false for all 1.1 or higher versions (this is the “Pessimistic  
Version Constraint” described at  
[http://docs.rubygems.org/read/chapter/16#page74](http://docs.rubygems.org/read/chapter/16#page74)  
if you want more).

-Rob

Rob B. [http://agileconsultingllc.com](http://agileconsultingllc.com)  
removed\_email\_address@domain.invalid