What is wrong with validates_presence_of :my_association ?

* Ben Johnson <rails-mailing-list@andreas-s.net> [2009-01-09 01:13:53 +0100]:

Category.has_many :products

Let's say a product must belong to a category. I know it is recommended
to do the following:

class Product
validates_presence_of :category_id
end

But, as we all know, this is a pain for new records, meaning what if the
associated category is a new record?

I've been meaning to ask this, but what's wrong with doing the
following:

class Product
validates_presence_of :category
end

In this case you may need validates_associated or write your own
validation by def validate.