Question

How do i validate a column in one table against entries in other tables?

The code I used to validate that the entry for column “:product_id” of table “Preperiod” exists in the column “id” of table “Product” is

validate :product_id_exists
def product_id_exists
 if Product.find_by_id(:product_id)==nil
   errors.add(:base, "Product must be defined")
 end
end

But now I get the error even when the product_id is right. What did I do wrong?

I use ruby 1.9.2 and rails 3.0.9

Answer 1

Product.find_by_id('here you should specify value of id field ... ') == nil 

so you your code should look like:

Product.find_by_id(product_id) == nil

or:

Product.find_by_id(self.product_id) == nil

or:

Product.find_by_id(self[:product_id]) == nil