rails/rails — pull request #7155 by robotex82 (2012-07-25 15:13:18+00:00)
Title: Added absence validator for active model.

Please accept my pull request for an absence validator.

See following discussion: https://groups.google.com/forum/#!topic/rubyonrails-core/KS_Olcnlw8w

I included passing tests and docs (Copied and adapted from the presence validator).

Thanks!

Saludos,

Roberto