Validates allow_nil not working as expected

I suspect this just doesn't work like I'm expecting it too, but if I use :allow_nil => TRUE, validation rules still complain if a form field is submitted empty (w/o using a presence_of rule).

So...

    validates_format_of :first_name, :with => Is_human_name,
       :allow_nil => TRUE, :message => Is_not_human_name_msg

Will complain if the field is submitted as empty. Now, empty doesn't conform to the regex I am using, but I am expecting that :allow_nil will cause the validation to be ignored when the value is empty.

(A) So what's the point of allow_nil? Or am I using it incorrectly?

Ultimately what I am trying to do is have certain messages override the need for others.

If I have this:

    validates_presence_of :first_name

    validates_format_of :first_name, :with => Is_human_name,
       :allow_nil => TRUE, :message => Is_not_human_name_msg

And the field is submitted as empty, then the only error message I need to see is the one that says the field cannot be empty. I do not need to see the format_of error message.

(B) What's the typical strategy for accomplishing that?

-- gw (www.railsdev.ws)

I'd drop the :allow_nil and use an :if => Proc.new { |model_name|
model_name.first_name.length > 0 }

Bulky, but it works. Thanks.

-- gw (www.railsdev.ws)

Turns out :allow_blank has been added for this very purpose...
http://dev.rubyonrails.org/ticket/7383

-- gw

true isn't upper case ... that may have been your problem - unless
you've defined a constant TRUE?