Rails - Dec 2005 - Verification problems

Hello,

Hope this isn''t a newbie question - but I don''t seem to be
able to find
relevent information elsewhere.

I am having trouble getting the following to work:
Schema
=====ActiveRecord::Schema.define(:version => 1) do

  create_table "authors", :force => true do |t|
    t.column "name", :string
  end

  create_table "books", :force => true do |t|
    t.column "title", :string
    t.column "author_id", :integer
  end

  create_table "catalogs", :force => true do |t|
    t.column "author_id", :integer
    t.column "book_id", :integer
  end

Models
=====class Author < ActiveRecord::Base
  has_many :book

  validates_uniqueness_of :name
end
class Book < ActiveRecord::Base
  belongs_to :author
  has_many :catalog

  validates_presence_of :author, :message => "doesn''t
exist!"
  validates_associated :author

  # Each book title must be unique to each author.
  def validate
    if Book.find_by_title_and_author_id(self.title, self.author_id)
      errors.add(:title, "(#{self.title}) already exists for this author 
(#{self.author.name})")
    end
  end
end
class Catalog < ActiveRecord::Base
  belongs_to :book

  validates_presence_of :book
  validates_associated :book
end


NOTE: The above is a contrived example to simplify the problem (in 
reality the Catalogs table has other data associated with it).

The problem is that you can add authors and books, and all the 
validation works like a charm (including checking the uniqueness across 
multiple columns for a book), but when I try to add something to the 
catalog, it is trying to validate the book model again and fails on the 
Book.find_by_title_and_author_id() as the book obviously already exists.

Why is rails trying to revalidate the Book model when I am adding 
something to the Catalog (it isn''t a save or update to Book is it?), am
I doing something wrong by checking uniqueness across multiple columns 
in the model (if I remove it all works, but then I end up with duplicate 
books).

Regards

Glenn

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

Glenn wrote:
> The problem is that you can add authors and books, and all the 
> validation works like a charm (including checking the uniqueness across 
> multiple columns for a book), but when I try to add something to the 
> catalog, it is trying to validate the book model again and fails on the 
> Book.find_by_title_and_author_id() as the book obviously already exists.
> 
> Why is rails trying to revalidate the Book model when I am adding 
> something to the Catalog (it isn''t a save or update to Book is
it?), am
> I doing something wrong by checking uniqueness across multiple columns 
> in the model (if I remove it all works, but then I end up with duplicate 
> books).
Perhaps you want either:

       validates_associated :book, :on => :create

or
       def validate_on_create
         ...
-- 
We develop, watch us RoR, in numbers too big to ignore.

>   # Each book title must be unique to each author.
>   def validate
>     if Book.find_by_title_and_author_id(self.title, self.author_id)
>       errors.add(:title, "(#{self.title}) already exists for this
author
> (#{self.author.name})")
>     end
>   end
This can be written as
validates_uniqueness_of :title, :scope => ''author_id''

See 
http://api.rubyonrails.com/classes/ActiveRecord/Validations/ClassMethods.html#M000685
for details.

-Ben

Benjamin Stiglitz wrote:
>>   # Each book title must be unique to each author.
>>   def validate
>>     if Book.find_by_title_and_author_id(self.title, self.author_id)
>>       errors.add(:title, "(#{self.title}) already exists for this
author
>> (#{self.author.name})")
>>     end
>>   end
> 
> This can be written as
> validates_uniqueness_of :title, :scope => ''author_id''
> 
> See
>
http://api.rubyonrails.com/classes/ActiveRecord/Validations/ClassMethods.html#M000685
> for details.
> 
> -Ben
Perfect - it works. Thanks for the tip.

Regards

Glenn

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