I.NFECTIO.US: Defining Numericality

Defining Numericality

Bob Silva — Fri, 27 Jan 2006 10:56:00 -0800

Now that I've been promoted to a management position, I don't get the opportunity to program as much as I'd like. I love sharing my knowledge of something I am passionate about and feel obligated to repay the debt I accumlated when I was learning how to program 10 years ago. So I monitor the Ruby on Rails mailing list for people in distress and throw on my cape and try to come to their rescue.

I had just such an opportunity last week, when this distressed soul wanted to validate that an input field was a positive integer.

This should be an easy one to figure out. validates_numericality_of sounds like the perfect remedy. As it turns out, validates_numericality_of only determines if its input is indeed a number. The only constraint you can specify is that its an integer as opposed to a decimal value.

My other choice would be validates_inclusion_of. Using the :in parameter to that method allows me to constrain the input value. I can specify that I want it to be within 0 and 4294967295.

validates_inclusion_of :int_field, :in => 0..4294967295

Not very pretty or intuitive. I got to wondering why this functionality couldn't be included in the validates_numericality_of routine. 'Numericality' is made up of 2 parts. 'Numerical' and 'ity'. We all know what 'Numerical' means (of or relating to numbers) and 'ity' is used to convert an adjective to a noun. Basically, it means we have a number. Therefore, 'Numericality' doesn't inherently constrain the value of a number, and in my opinion, neither should validates_numericality_of.

:validates_numericality_of :my_positive_integer, :gte => 0

Problem solved. You can download this plugin, which extends validates_numericality_of with 7 new options:

:gt - Greater than
:gte - Greater than or equal
:eq - Equal to
:lt - Less than
:lte - Less than or equal
:even - Even number
:odd - Odd number

Another lost soul rescued and now I must hang up my cape, return to my regular job and wait for another opportunity to jump into action.

UPDATE: This has been submitted as a patch against trunk.
http://dev.rubyonrails.org/ticket/3952

"Defining Numericality" by PMc

Thu, 22 Feb 2007 15:07:16 -0800

There is some strangeness here:
1.
A not-equal operator is missing. I do not see the real sense in an equal operator - if there should be a predefined specific value for a field, then why open a field at all? But I see lot of sense in a non-equal operator, especially in each shopping system you do not want an item-count 0 entered.
2.
There is no longer checked against general numericality as soon as there is a comparison added. I do not see why an erroneous entry like maybe "19%0" should still be compared but not be detected as erroneous.
3.
If I request ":gte => 2.5" and enter 2.5, I still get an error. This is obvious from the code, as there is a conversion to_i done. I do not see why.
4.
As soon as one of the comparisons is used, the error message given by :message is no longer used, instead a static one from the plugin is used.
5.
I do not understand the code.

"Defining Numericality" by yves_dufour@mac.com

Wed, 11 Oct 2006 08:16:30 -0700

Why it's not possible to write ? :validates_numericality_of :my_integer1, :gte = 0 :validates_numericality_of :my_integer2, :gte = :my_integer1 would be a must.... yd

"Defining Numericality" by Problems

Tue, 22 Aug 2006 02:15:00 -0700

I am running into trouble with the 'gte' and 'lte' operators somehow they fail to work. The error message doesn't seem to be added to the error messages for those operators. I am not sure what exactly is the problem. The other operators work just fine.

"Defining Numericality" by Awesome!

Mon, 31 Jul 2006 19:36:02 -0700

Thanks! I came across the RoR mailing list post about this first before stumbling upon this article from a slightly different Google search.

"Defining Numericality" by Great!

Mon, 31 Jul 2006 13:23:36 -0700

Thanks for this simple plugin, it's really cool!