Nested validations

Rails 2.1 lacks support for easy nested validations so that multiple validations on the same field dont all show up at once.

It would be nice to have something like this for example.

validates_presence_of :username do

validates_format_of :username, :with => /[A-Za-z0-9]+/ do

validates_uniqueness_of :username, :case_sensitive => false

end

end

In this case, uniqueness would only be run if format validates, which would only be run if username is present.