Rails - Jul 2006 - Newbie validation question

I am having problems with a validation, the full model code is below.

The validate routine is attempting to see if another record with the 
same artist_name, title, & catalogue_no exists in the products table. If 
so, it should throw an error.

This is the validation code:

def validate
  if Product.find(:all, :conditions => ["artist_name = ?, title = ?, 
catalogue_no = ?", artist_name, title, catalogue_no])
    errors.add(:title, "This title already exists, artist: " + 
artist_name.to_s + ", title: " + title.to_s + ", catalogue
number: " +
catalogue_no)
end

When I use Product.find I receive this error:

Mysql::Error: #21000Operand should contain 1 column(s): SELECT * FROM 
products WHERE (artist_name = ''Jimmie Rodgers'', title =
''Rodgers'',
catalogue_no = ''38134'')

I have tried self.find & I receive this error:
undefined method `find'' for #<Product:0x38137d8>

I think I understand why both occur, but I am now at a loss as how to 
achieve my desired functionality.

Any help would be greatly appreciates, also it would be great to have 
some outline to me why Product.find & self.find bring throw errors.

rgds,
- matt

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

class Product < ActiveRecord::Base
	belongs_to :label
	has_many :tracks

	validates_presence_of :country, :title, :catalogue_no, :release_date, 
:format, :barcode, :disc_no, :genre_main

	validates_uniqueness_of :catalogue_no

	def validate
	  if Product.find(:all, :conditions => ["artist_name = ?, title = ?, 
catalogue_no = ?", artist_name, title, catalogue_no])
	    errors.add(:title, "This title already exists, artist: " + 
artist_name.to_s + ", title: " + title.to_s + ", catalogue
number: " +
catalogue_no)
	  end
	end
end

-- 
Posted via http://www.ruby-forum.com/.

Matt,

Valid SQL statement is:

Product.find(:all, :conditions => ["artist_name = ? AND title = ? AND
catalogue_no = ?", artist_name, title, catalogue_no])

Jean-Etienne

-- 
Posted via http://www.ruby-forum.com/.

Jean-Etienne wrote:
> Matt,
> 
> Valid SQL statement is:
> 
> Product.find(:all, :conditions => ["artist_name = ? AND title = ?
AND
> catalogue_no = ?", artist_name, title, catalogue_no])
> 
> Jean-Etienne
Many Thanks, all works fine now - your response time was nothing short 
of amazing.

-- 
Posted via http://www.ruby-forum.com/.

Matt Stone wrote:
> I am having problems with a validation, the full model code is below.
> 
> The validate routine is attempting to see if another record with the 
> same artist_name, title, & catalogue_no exists in the products table.
If
> so, it should throw an error.
> 
> This is the validation code:
> 
> def validate
>   if Product.find(:all, :conditions => ["artist_name = ?, title =
?,
> catalogue_no = ?", artist_name, title, catalogue_no])
>     errors.add(:title, "This title already exists, artist: " + 
> artist_name.to_s + ", title: " + title.to_s + ", catalogue
number: " +
> catalogue_no)
> end
Take a look at the documentation for validates_uniqueness_of

http://api.rubyonrails.com/classes/ActiveRecord/Validations/ClassMethods.html#M000816

This might work (in Product):

   validates_uniqueness_of :catalogue_no,
                           :scope => [:artist_name, :title]

regards

   Justin