validates_uniqueness_of where scope euqals created_by "magic" field

rubyonrails-talk
1

I have the following ActiveRecord objects:

class Recipe < ActiveRecord::Base   has_many :ratings, :dependent => true   . . . end

class Rating < ActiveRecord::Base   validates_uniqueness_of :created_by, :scope => :recipe_id   belongs_to :recipe, :counter_cache => true   . . . end

The created_by field on Rating is implemented as a "magic" field similar to this: http://wiki.rubyonrails.org/rails/pages/Howto+Add+created_by+and+updated_by. It is working fine.

The validates_uniqueness_of :created_by, :scope => :recipe_id isn't working. I can easily go about adding multiple Ratings per Recipe for a user. Maybe I'm missing something here, but what I want is to make sure that a user can only add one Rating per Recipe. I'm guessing that the created_by field is null when the validation runs, and then is populated by the current user when the record is saved. Can anyone shed some light on this and perhaps point me to a better solution?

Thanks,

JB

2

Probably hack-ish, but you could manually set the created_by field before you save.

JB wrote:

3

Thanks. I tried that, but for some reason the validate doesn't seem to be running. I'm still getting duplicates.

If I add an index to the fields at the database level, then Rails throws a duplicate record exception.

I wonder if it has something to do with one of my belongs_to declarations. My entire Recipe model code looks like this:

class Rating < ActiveRecord::Base

  validates_presence_of :recipe_id, :value   validates_numericality_of :value, :only_integer => true   validates_uniqueness_of :created_by, :scope => :recipe_id

  belongs_to :recipe, :counter_cache => true   belongs_to :created_by, :class_name => "User", :foreign_key => "created_by"

end

Jason Norris wrote: