# \[ActiveRecord::validations\] check CNAME or Empty

**URL:** <https://www.ruby-forum.com/t/activerecord-validations-check-cname-or-empty/132545>\
**Category:** Rails\
**Created:** [March 21, 2008, 9:32am UTC](https://www.ruby-forum.com/t/activerecord-validations-check-cname-or-empty/132545 "2008-03-21T09:32:06Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![evaisse](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/bb73d2/32.png) [@evaisse](https://www.ruby-forum.com/u/evaisse)\
**Post date:** [March 21, 2008, 9:32am UTC](https://www.ruby-forum.com/t/activerecord-validations-check-cname-or-empty/132545/1 "2008-03-21T09:32:06Z")

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Hi I wanna check in my model if the field is conform to a CNAME OR is  
empty

I’ve put something like this in my model :

validates\_format\_of :cname, :with =\> /^[a-z0-9-]+$/i,  
:unless =\> :cname.strip == ‘’