Rails - Sep 2005 - Another validation question

I want to prevent people from adding patient into the database with
the first_name and last_name reversed when it already exists in the
database.

E.g -  

First user correctly adds "Cindy Tompkins" to the database

Second user attempts to add "Tompkins Cindy" because he mixes up the
last_name and first_name fields on the form and didn''t notice that the
person was already added to the database.

-----------------------

This scenario happens frequently because some people naturally think
"Last Name first" and others "First Name first" and there
will be
inconsistencies despite clear instructions on the page.

How do I use validate to prevent this?

Thanks,
Dewey

Hi !

Dewey Howell said the following on 2005-09-03 22:23:
> First user correctly adds "Cindy Tompkins" to the database
> 
> Second user attempts to add "Tompkins Cindy" because he mixes up
the
> last_name and first_name fields on the form and didn''t notice that
the
> person was already added to the database.
> 
> -----------------------
> 
> This scenario happens frequently because some people naturally think
> "Last Name first" and others "First Name first" and
there will be
> inconsistencies despite clear instructions on the page.
> 
> How do I use validate to prevent this?
Use a validation helper method:
class Patient < ActiveRecord::Base
   validate :first_last_uniqueness

private
   # Checks that first, last and last, first are unique
   def first_last_uniqueness()
     self.errors.add(:first, ''First and last must be unique'')
if
         self.find(:first,
               :conditions => [''last = ? and first = ?'',
                   self.last, self.first])
     self.errors.add(:first, ''First and last must be unique'')
if
     self.find(:first,
               :conditions => [''first = ? and last = ?'',
                   self.last, self.first])
   end
end

WARNING: Untested code

In fact, you can write any method, and you add to the errors collection 
to do your validation.

Hope that helps !
François

On 9/3/05, Dewey Howell
<deweyhowell-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> I want to prevent people from adding patient into the database with
> the first_name and last_name reversed when it already exists in the
> database.
I''d urge you to think two or three times before doing this.  There are
about a billion valid counter-examples, like Patrick James and James
Patrick.
Do you have something else you could check against, like street
address, e-mail address, etc, etc?  Not sure what kind of application
you''re talking about.
The demographic data I''m usually working with would instantly break
this validation.