Rails: _destroy attribute in a nested model skips validates_presence_of

I'm following the Nested M开发者_Python百科odel Form Part 1.

But I have one problem.

If I add validates_presence_of :answers:

class Question < ActiveRecord::Base
 belongs_to :survey
 validates_presence_of :answers
 has_many :answers, :dependent => :destroy
 accepts_nested_attributes_for :answers, 
        :reject_if => lambda { |a| a[:content].blank? },  
        :allow_destroy => true
end

The _destroy skips the Question model validation. So I can update the Question model with empty answers.

I'm probably doing it wrong. How can I fix it?

Thanks in advance.

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I'm thinking you do not want to :validates_presence_of :answers, I think you want :validates_associated :answers which will run Answer's validations.

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I've also asked this question and found the answer.

This link describes the problem better (from my question) and has the answer to it too. http://homeonrails.com/2012/10/validating-nested-associations-in-rails/

Basically he rejected those that are marked for destruction and counted the remaining ones.