Rails - Apr 2006 - DRY validation

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Hi all,

A few months ago someone posted a message about specifying validates_*
constraints on a per-attribute basis.  I just created a small plugin  
that
allows you to do this.

Here''s an example from one of my models:

   class Country < ActiveRecord::Base
     attribute :name, :string do |a|
       a.validates_length :within => 1..48
       a.validates_format :with =>
/\A[A-Z](?:\s*[''\(-]?[A-Za-z]+[,\.
\)]?)*\z/
       a.validates_uniqueness
     end

     attribute :code_alpha2, :string do |a|
       a.validates_length :is => 2
       a.validates_format :with => /\A[A-Z]+\z/
       a.validates_uniqueness
     end

     attribute :code_alpha3, :string do |a|
       a.validates_length :is => 3
       a.validates_format :with => /\A[A-Z]+\z/
       a.validates_uniqueness
     end

     attribute :phone_code, :integer, :allow_nil => true do |a|
       a.validates_numericality :greater_than_or_equal_to =>  
1, :less_than_or_equal_to => 9999
     end
   end

The advantage of this it DRYs up the validation rules since you
don''t have to specify the name of the attribute over and over.
Plus it automatically sets validates_presence_of for the attribute
unless you set allow_nil as true -- as shown in the phone_code
attribute above.

The plugin can be downloaded from here:

   http://onautopilot.com/oss/rails/active_attribute.tgz

One nice extra benefit is when I rearranged my validation rules
on a per-attribute basis I found a few attributes I forgot
to validate.  I used the annotate_models plug to add a list of
every column to the top of my model, and proceeded to add
validation rules for each of the forgotten attributes.  It
turned out to be a nice way to make sure the bases were better
covered.

So anyway, give it a shot and let me know how it works
out for you.

- --

Thanks,

Dan
__________________________________________________________________

Dan Kubb
Autopilot Marketing Inc.

Email: dan.kubb@autopilotmarketing.com
Phone: 1 (604) 820-0212
Web:   http://autopilotmarketing.com/
vCard: http://autopilotmarketing.com/~dan.kubb/vcard
__________________________________________________________________



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