Validations :allow_empty feature

So, here's a case something didn't work as expected, and I'm wondering
if a feature tweak is worth considering.

If I use :allow_nil => TRUE, validation rules still complain if a form
field is submitted empty (w/o using a presence_of rule).


   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 was expecting that :allow_nil
will cause the validation to be ignored when the value is empty.

After thinking about it, I can see that params creates emptry strings
which are not interpreted as nil for saving. That makes sense, and
therefore I can see why Rails still validated my format rule.

Ultimately what I was trying to do was 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, or another any subsequent rule failure
that might apply.

It was suggested that using an :if is the typical strategy for
accomplishing that:

   :if => { |model_name| model_name.first_name.length > 0 }

That seems rather bulky (especially when repetitive), and I wonder if an
:allow_empty => TRUE couldn't be used to provide the behavior I was
expecting -- rules are ignored for *empty* fields, not just Nil ones.

Or perhaps it is better named, :ignore_empty => TRUE

Maybe this is too small a use case, but it sure reduces the :if bulk.
Just a thought...

:allow_blank is in 2.0 AFAIK, so that should do what you want

Andrew Kaspick wrote:

:allow_blank is in 2.0 AFAIK, so that should do what you want

Ah. Yep. a search for allow_blank reveals

Didn't catch that with my other searches.

If I use :allow_blank => false I expect that no blanks are allowed,
however, they are allowed.

def test_validates_length_of_with_no_allow_blank

Topic.validates_length_of( :title, :maximum => 5,

:allow_blank=>false )

assert !Topic.create("title" => "abcdefg").valid?

assert !Topic.create("title" => "").valid?

assert !Topic.create("title" => nil).valid?

assert Topic.create("title" => "abcde").valid?


This test fails on the 2nd assert.

The default validation options include :allow_nil=>false and
:allow_blank=>false. I suggest those are removed, and only when
those options are explicitely passed into the options hash of one of
the validate methods would you check for allow_nil and/or allow_blank.

Futhermore, now that we have the :allow_blank option, does anyone
understand why validate_presence_of can’t use validates_each? And why
does that method need to be able to deal with “nonexistent attributes”
and all the other validate methods not ??