# Regular Expressions

**URL:** <https://discuss.rubyonrails.org/t/regular-expressions/295>\
**Category:** rubyonrails-talk\
**Created:** [August 23, 2006, 6:13am UTC](https://discuss.rubyonrails.org/t/regular-expressions/295 "2006-08-23T06:13:04Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Hasan\_Diwan](https://avatars.discourse-cdn.com/v4/letter/h/a3d4f5/32.png) [@Hasan\_Diwan](https://discuss.rubyonrails.org/u/Hasan_Diwan)\
**Post date:** [August 23, 2006, 6:13am UTC](https://discuss.rubyonrails.org/t/regular-expressions/295/1 "2006-08-23T06:13:04Z")

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validates\_format\_of :r\_or\_s :with =\> /^(r|s)$/, :on =\> :create